From this thread:
http://www.bricklink.com/message.asp?ID=292018

I've found that one dead give-away with an underage buyer/seller is
that they have an uncanny desire to tack their age onto the end of
their username. So if you ever see a user name with like Something15
or Something13...yeah, 10 to 1 says it's a tweenager trying to play
adult.

--

Onideus Mad Hatter
mhm ¹ x ¹
http://www.backwater-productions.net
http://www.backwater-productions.net/hatter-blog

Hatter Quotes
-------------
"You're only one of the best if you're striving to become one of the
best."

"I didn't make reality, Sunshine, I just verbally bitch slapped you
with it."

"I'm not a professional, I'm an artist."

Check this out:
http://www.bricklink.com/message.asp?ID=292455

http://www.bricklink.com/store.asp?p=wahiggin&itemID=11192283

...he's trying to sell just the ONE minifig for basically $20...now,
um, anyone who isn't plainly retarded knows that the set she comes
with:
http://shop.lego.com/ByTheme/Product.aspx?p=7886&cn=39&d=70

...only costs $30, so why would anyone in their right mind pay nearly
2/3rds of the cost of the original set just to get ONE of its
minifigs?

I mean I could ~maybe~ understand it if the set was no longer being
sold, and I think that the other guy selling them, for about fifty
cents more who has like 56 of them certainly has that as his intended
goal. But to pop off in the forums, practically fondling yer balls
and trying to make it sound as if yer selling something absolutely
INCREDIBLE at a WHOLE 50 cents lower than the other TWO people selling
them on BrickLink WHILE the set is STILL being openly sold on Lego's
website for only $10 more...yeah...I don't think the greater fool
theory runs *THAT* deep.