Bitcoinica, Mybitcoin, inputs.io... Trusting people with your funds in this game has gotten many people burned. There isn't, and can't yet be, a single operator out there who could truly be trusted. No exchange has even been running long enough.
Personally, I have a lot of faith in Bitstamp, for example, but I don't trust them implicitly. Spectacularly trustworthy people have stolen or simply lost other people's money time and time again, and I'm sure we'll see big losses in the future as well.
Edit: To be clear, right now, I don't think Bitstamp is doing anything alarming. I have gotten everything I was supposed to get out from there promptly, so the "technical issues" explanation seems credible to me.