Easily everyone's biggest mistake was not buying or mining sooner, so I guess your question is really about our second biggest mistakes?

In my case, that's easy. I issued an international wire transfer for many thousands of USD to BTC-e at the beginning of November, to get in on the jump we all knew was coming. I'm still waiting for those funds to be credited to my account. I assume BTC-e are using it for their own purposes, and having a big laugh at my expense. I've started calling this practice of theirs charging people for the privilege of giving BTC-e an interest free loan.

I surely won't do that again. My bank will soon issue a chargeback on those funds. I've heard this story again and again, so maybe it's my fault for thinking it wouldn't happen to me. Maybe my timing was just bad: these stories seem to have multiplied since.

All my transactions since have been on Coinbase, and I couldn't be happier.

- Findiggle.