The rumour surfaced earlier this week, and the idea's been bandied about for a while, but it's finally happened: with the latest Uber Update, Team Fortress 2 has gone free to play FOREVER.
Valve’s Robin Walker assured that Team Fortress 2 would only be monetised by microtransaction payments.
No advertising model will be pursued, Walker said. No premium subscription model will be used. No cynical “pay-to-win” options will be implemented, he assured.
A few games have switched to a free-to-play model, most notably MMOs like Lord of the Rings Online. Old first-person shooters have been spit-shined and turned into F2P games as well, like Quake Live and Battlefield Play4Free (built on a modified version of and containing content from Battlefield 2).