I used to belong to a service like that called askme.com where people would sign up as experts on a subject and then answer questions submitted by people who needed the information. The problem I found on the site - and all sites like it that I've seen since - is that you get too many know-it-alls that really don't know squat. Oh, they talk a good game, but to the "experts" who really are experts, it becomes obvious rather quickly who the charlatans are. The problem is that those seeking help don't.

An extreme example of how bad the advice on these types of sites can be is on askme.com there was a fellow who claimed to be an expert in somewhere around 40-50 areas. I was reading his advice to one person which, if followed, would have cost that person at least $10K to fix the problems caused by the moron's advice. There were several experts that continually complained about this "expert's" advice, yet because he was so active, the company allowed him to continue posting crap.

This problem exists on forums as well. There are always a few know-it-alls that post far too often about things they think they know. I got in an argument on a website design forum with a fellow who had no idea of the reality of copyright law and simply kept stating his opinions as fact. It was quite obvious that the guy thought "this is the way I think it should work, so I'll state it as truth."

The caveat is: Caveat Emptor! There are charlatans out there and a lot of people who never grew out of the teenage "I know everything" mental process.

On a nice aside, I've not found an obvious know-it-all on this site. I've read some very opinionated posts, but the forum members have the maturity to qualify statements with phrases such as "in my experience" and "what's worked for me is..." Maybe it is that because we are photographers - and photographers are artists - and artists tend to have the belief that we can always learn more and improve - we are by nature slightly more humble. Of course, it could simply be that this site has pulled in a more mature fellowship than many sites and forums.

Of course, all of this is IMHO. 

Jeff