Valve has pissed off many veteran Team Fortress 2 players with the Uber Update. The biggest thing the Uber Update brought to TF2 was a massive increase in activity, but that irked many of the people who paid $20-$60 for the game in the past four years.
I myself just started playing TF2 about five months ago (My Steam ID is SolidSean, if you want to play), and I payed $20 for it, and have no problem that it is now free. The TF2 veterans are acting like a bunch of grumpy old men looking for anything to complain about. One can only assume they are trying to get some sort of compensation from Valve, which is undeserving. The increased activity, more populated servers, and potential increase in challenge for all skill levels is the only compensation I see fit.
Killzone 3 is one of my favorite games to play online, and lately I haven't been playing it much, mostly due to a backlog, but if Sony came out tomorrow and said that it is now free for everyone to play, I'd probably hop back on. I wouldn't be pissed, and that game came out just four months ago.
Basically, if you're bitching about a game becoming free years or months after you paid for it, shut your mouth, and if you don't want to shut your mouth I suggest waiting years and years before buying any game, in hopes that it too becomes free.