Regrets:
Selling most of the BTC that I mined in 2011 and 2012.
Trusting Andrew "shakaru" Nollan too much (he still owes me $200).
Some BTC<->fiat trading decisions.

With all the other scams and hacks I was actually quite lucky, I don't trust others easily and I often wait some time (days, weeks or months) before trying new services or otherwise parting with my BTC. And very often just when I am almost ready to send some money a service/exchange/security turns out to be a fraud/gets hacked/aliens attack/whatever.

EDIT:

My reply in a similar thread:

Not having found bitcoin earlier!

Sleeping through the $266 bubble.

But the good thing is humans are so full of regrets that we can list a new one in each thread. With enough threads we'll get to them all eventually.

Here's another one: Accepting the free btc from Bitcoinica for signing up. That eventually cost me.

But we have to look back. It improves our future. Would anyone today put all their btc in an online wallet that could be hacked or stolen by the operator? Oh yeah, they're still doing it.... never mind.

Sending 25 bitcoins to the wrong instawallet address. Dumb dumb dumb.

Not buying ASICminer shares at 0.01BTC when I had the chance.

I mean, I could spend a year whining about not mining in 2011, but I wasn't even involved in Bitcoin back then so that's that. But the shares, I was there and I was thinking about buying.

glbse

join this community and field very late its feel biggest bitcoin related mistakes 

biggest mistake was that i thought mtgox/bitcoin was scam and shoved it all into the garbage bin after purchasing 100 btc in june 2011 shortly before bubble burst and my mtgox account got hacked.

in the 2nd half of 2011 i happened to have 30 k € to invest. choosed gold & silver.

so i actually was on track to make a fortune but got discouraged so deeply that i forgot all about this "scam".