Some wonderful, logical arguments against declawing can be found here.
http://www.littlebigcat.com/index.php?action=library&show=002

This is a list of countries where the procedure is illegal.
http://www.declawing.com/list.html

This page lists the things that can go wrong during a traditional
(guillotine/scalpel cuts last half of bone that has claw) declaw
surgery.
http://www.moggies.co.uk/stories/declaw.html

The things that can go wrong are multitude. If they choose to declaw
despite all you've said, they need an experienced vet who can perform
the amputation of the full last bone with a laser. This is the newest
technology and the newest procedure; it costs more, but has far less
complications and pain than the traditional mutilation, as it doesn't
actually cut bone - it separates the bones at the joint. This eliminates
the possibility of bone/claw regrowth sometimes seen in traditional
declaws.
It is still the equivalent of getting your toes cut off and trying to
walk around, though. A cat doesn't get a wheelchair. It has to walk
around on the amputated ends of its toes the very day after surgery.

And my favorite quote.
[quote]
Dr. Nicholas Dodman, Professor of Behavioral Pharmacology and Director
of the Behavior Clinic at Tufts University School of Veterinary Medicine
and internationally known specialist in domestic animal behavioral
research, explains declawing:

"The inhumanity of the procedure is clearly demonstrated by the nature
of cats' recovery from anesthesia following the surgery. Unlike routine
recoveries, including recovery from neutering surgeries, which are
fairly peaceful, declawing surgery results in cats bouncing off the
walls of the recovery cage because of excruciating pain. Cats that are
more stoic huddle in the corner of the recovery cage, immobilized in a
state of helplessness, presumably by overwhelming pain. Declawing fits
the dictionary definition of mutilation to a tee. Words such as deform,
disfigure, disjoint, and dismember all apply to this surgery. Partial
digital amputation is so horrible that it has been employed for torture
of prisoners of war, and in veterinary medicine, the clinical procedure
serves as model of severe pain for testing the efficacy of analgesic
drugs. Even though analgesic drugs can be used postoperatively, they
rarely are, and their effects are incomplete and transient anyway, so
sooner or later the pain will emerge."  (Excerpted from The Cat Who
Cried For Help, Dodman N, Bantam Books, New York).
[/quote]

Here are some tips I collected to help them scratch properly

1. Hopefully he likes catnip. If so, rub it all over the scratching post.
Scratch the post yourself, if he still doesn't use it, take his little paws and
scratch the post with them and tell him he's a good kitty. Remember to
associate positive things with acceptable clawing and negative things with
unacceptable clawing.

2. Try a scratching mat. Some prefer horizontal over vetical surfaces.

3. Try sisal, rug, cardboard, fabric... covered trees or mat. You can get cheap
thin door mats and staple gun them to a cat tree. Use canvas if he really likes
fabric. Be sure the stapes go vertical like this "|" and not horizontal like
this "--" so they don't get their claws stuck in there.

4. Put double sided tape where he likes to scratch. They won't like the
stickiness. They may then scratch a few inches over from the tape so be
prepared to add more. Keep no. 5 in mind when using the tape.

5. Don't let him in that room where he scratches when you're not around. When
you're around stand gaurd with a squirt gun and squirt him from a distance when
he scratches the furniture. If he's real persistent, put a little bit of
vinegar in the squirt gun. You can also yell "NO!" when he scratches there. I
also like to take him away from that area instantly and take him to the
scratchy tree, hold his paws and help him scratch while praising him. Make it a
fun experience, don't hold him forcefully or he'll fear the kitty tree. Make
everything associated with the kitty tree positive. I sometimes will put a
scratchy tree close to the furniture they are clawing so they have a nearby
alternative.

6. Put vinegar where he scratches. They don't like the smell.

7. Try some of that cat away spray.

8. Try a scat mat where he is scratching.

9. Get rid of fabric furniture with vertical fabric sides. Get THICK leather or
wood sofa and chairs.

10. Try soft paws.

11. Try trimming his claws every ten days. Some do once a week.

12. Whenever you see him clawing appropriately, praise and reward him lavishly.
Continue to praise him forever or he may get lazy.

13. Try Feliway to calm them down.

14. Make sure your cat tree is tall and heavy enough. Big kitties will topple a
small light one with a small base. I put weights on the bottom of mine. I get
the big ones. I also have a multi-tier cat tree they like to rip up.

15. Try this product, a cat tree that attaches to the side of your couch.
http://www.birminghamind.com/Scratchaway/index.html

I have a good article link in my signature.  Did you have this people sign any
kind of contract when they adopted the cat?  If you didn't, for future
reference you should always include a clause that the cat is not to be
declawed.  That way you could have taken him back.  But I know we don't always
think of these things beforehand.  I really hope you can convince these people
not to declaw the poor kitty :(

Lauren
________
See my cats:  http://community.webshots.com/album/56955940rWhxAe
Raw Diet Info: http://www.holisticat.com/drjletter.html
http://www.geocities.com/rawfeeders/ForCatsOnly.html
Declawing Info: http://www.wholecat.com/articles/claws.htm

<snip for space>

For people who argue that they can't train the cat not to scratch, I
recommend Soft Paws.  If they are able to trim his nails, they can put them
on.  The Soft Paws website also has a lot of info about declawing.  I agree,
it's best to remain calm and collected when presenting the declawing info to
them.  They sound like the type of people who may be able to be turned
around on it.  They probably have no idea what's involved.

I took in this feral cat, and scratch-training was effortless.
I wonder if they're just looking to throw money at it.

My mom adopted a cat that was already declawed.  It's hideous.  It
walks around on these stumps as if it still hurts (maybe it does).

It's front paws are so horrible, and every toe is a different length,
and the front paws are half the size of the rear.

What do they charge for this "procedure," because I'm pretty sure I
could do the same job with wire cutters.