The right hacker can hack anything.
To say they can't based on one event?
Steam is shit. Too slow, too autonomous. I dunno about bug-ridden. It's never crashed.
I don't agree with a required install of any secondary software. You want to check for CD, fine. CD Key, fine. But I don't register, I don't auto-download, and I certainly do not install secondary software to install a game. That's too Macintosh. And this is not iValve.
If I use Steam to purchase software, I'll firstly need a credit card. Secondly the will, or want to use that card. And Thirdly the assurance that I will always have broadband internet near my computer.
...?
I'll stick with cash. If I was to download anything from purchase, I had better be able to burn it to a disc or three, thusly I will retain a hardcopy for bad times.
That would make me consider online autonomous download purchase service (someone give this shit a buzzword!).