A friend of mine has her pics being used by agencies she has never heard of as well as a few she has been associated with for a short period of time in the past.
Her requests to have them taken off their websites have been ignored or acknowledged with a promise which is then unkept.
What can she do about this legally. Would a letter from a lawyer do any good? I might ad, she was a candidate for Playboy Playmate so I imagine the lowlife agencies just look at her pics as part of their marketing plan.
This is a common problem I know and would welcome any advice I can get for her.
Thanks for everyones' help on this.

Then have her attorney write the agency/person. Of course that is assuming her photos are copyrighted.

If you really wanted to be her knight in shining armor, you could do some turnabout play.

Wateremarking might be defeatable with sufficient effort, the point is to make it enough of a bother that they steal someone else's without it.  
This has come up on the Legal Board in the past & I think an Attorney's demand letter was helpful in getting it removed.
skb

The only way to get it out is by cropping it out. If you put it in a prominent position it becomes pointless to bother. My ol' lady used to stamp her contact e-mail addy right across the middle of her photos. If someone were to crop it out, they'd be removing all of her more desireable assets from the photo along with it, thus making it pointless. Never had a problem with photo theft again.

After polite requests get ignored, it's time to break out the big guns.

Its all helpful, and a special thanks to Carrie for the link to the Jenny DeMilo narrative on the issue located in the link she gave us to the previous TER thread.
Appreciate it very much.

to find out the name of the hosting company, this is easily done using Whois, then send the hosting company an email saying that such and such site is using her pics without authorization. It is in their Terms of Service that sites cannot post copyrighted pics without permission. They will suspend the site from their server or advised the owner of the site to remove such pictures to avoid suspension.