I hate to say it, but I have used all three of those services without any sort of problem, is it possible that your computer has had a security breach?
I had no problem either, until I did.
isn't this like saying "hey, I also drive a car and I have never had an accident"?
I seriously doubt my heavily firewalled with encrypted FS (where my bitcoin info is) linux is compromised, but even if it was, the 2nd password on blockchain uses a virtual keyboard to thwart keyloggers. But more to your point, I have taken steps to insure my security locally. Really, it is just blockchain that shocks me. BTCE has been hacked up one side and down the other (a google search will confirm this, no flames please), and bitcoin-24 was flirting with legal disaster from the beginning, so loosing money to those guys is not a big surprise.