If you encounter a problem with agencies collecting on illegitimate debt, it may be reported to the credit bureaus, which can be a big deal for you (buying home, etc).

The bureaus wont help you; I went through an 18-month ordeal figuring out how to clear these things, and heres what I suggest:

-get up to speed on FDCPA rights -officially dispute the collection -pursue the original debtor, and get a resolution in writing. sue them in small claims to get a judgement in your favor if you need to. -send a copy of the resolution to the debt collector and the credit bureau dispute centers

Hope this helps in case anyone is dealing with this kind of stuff.