When people here ask "Which is the best hotel/restaurant/etc?" do you give them your true opinion? Even knowing that the information will be made public on this board, and perhaps cause your favorite place to be overrun with tourists? Just wondering...

Yes. I tell people the truth because when I am asking and people give me good advice, I like to reciprocate.

Any experienced, well traveled and frequent contributor to any of Fodor's forums will be honest in his opinion if he wants to be taken seriously. If he's not, he'll be readily exposed by those with vast knowledge and experience.

Having said that, anyone who says a particular restaurant is the "best" is not to be taken too seriously. If a New Yorker says that restaurnat "ABCDE" is the best, does that truly mean the best of New York's 17,000 restaurants ranging from five star dining experiences to greasy spoons, all of which he's tried in order to identify the best? Has he slept in every room in every hotel in New York to determine the "best"? What are his credentials for knowing what is "best"?

The truly useful advisor is the one who suggests accommodations or dining experiences based on his subjective opinion and expresses his reasons for that opinion.

Of course I alway am honest and I expect the same from others. We are here to help each other....RIGHT?

Yes, I always give my true opinion and I never tell to not stay in a certain hotel or do not eat in some restaurant even if I had an unpleasant experience. I also do not say you must stay in this hotel or you must eat in that restaurant. I try to tell what was my personal experience. My expectations may be very different than yours.
For example, we loved our stay in Dimitsana, Greece. How many Fodorites do you think will plan their trips based on my statement? I do not think that because of my statement Dimitsana will suddenly become overrun with visitors.