If they were to go bankrupt ....
You won't be able to purchase new games etc through if this was to happen.
You can Still play all your games.
The activation is a 1 time process.
True, Steam needs to be running to play the game. However, it does NOT need to have a internet connection in order to play your games. (with the exception of downloading patches, friends, chat etc)
You can set it to offline mode after the initial activation occurs
I get it, i do. I used to dislike STEAM as well. After getting used to it, and doing business with them a while, I grew to like them and even prefer them as digital distributor.
Look at it as sort of a disc check so to speak, only you dont really need the disc.
I prefer to stay online though for many reasons, & because the ingame browser is a bit easier than ALT+Tabbing out of the game. just [censored]+TAB and you have everything you need

Im still waiting for UPS Grrrrrrrrrrr