One of the highest hurdles for any unpublished author to overcome is finding an agent. I know that I have been incredibly fortunate to be taken on by the first agency that I approached, and also to have such an excellent working relationship with them. Of course we have not got as far as securing a publishing contract, but their record speaks for itself: if Lord Alexander's Cipher; or, the Bridekirk Behemoth does not find a publisher it won't be because Ampersand aren't any good.
Not everybody is so lucky, and many aspiring writers are desperate to find an agent. So desperate that they are at risk of falling for scams. This seems to be a bigger problem in the US than over here, but the US is also where you will find operations like Writer Beware which exist to expose such scam-merchants for what they are.
Of course not all scammers are happy with the exposure that they get on websites like Writer Beware's Twenty Worst Agents list. One agent on this list, Barbara Bauer, has even started making legal threats against websites that highlight her place on that list. This has sometimes worked, but more often stirred up further negative publicity.
In addition to the Writer Beware list, there is also the venerable Preditors and Editors, who can be relied upon to draw attention to scammers (see what they say about Barbara Bauer). And for those of you looking for the personal touch, a post like this would not be complete without a reference to Gerard Jones and his snappily titled site, Everyone Who's Anyone in Adult Trade Publishing, Propagandaville and Tinseltown, Too, is a Worthless, Superfluous, Giddy, Giggly, Chickenhearted, Money-Grubbing Nazi Moron.