I think the best place to post a message of thanks is in the thread where the information was first requested. It gives a feeling of completion to a thread, telling everybody that requested information was received and that it was satisfactory - kind of a signal that people can now stop looking. This seems to be what usually happens, but then there are other times when somebody requests information and people bend over backwards to get it - and we never hear a word from the original requester.
Sometimes, I will e-mail information to a requester, and I'll usually get thanks back by way of e-mail. Maybe should I go back to the thread and post a message to say the information has been received and appreciated?
-Joe Offer-