Semi-via the neeto Steam Review, I spotted a Brazilian site named 'Online Gaming Zeitgeist', which is particularly handy because it uses GameSpy's online server list for many popular PC FPSes to create graphs over time of game popularity - revealing plenty of interesting trends!

Though it doesn't try to be canonical (and there are plenty of caveats involved from just using GameSpy's lists!), there's an interesting post about 'The Christmas Effect' which reveals of the holiday PC game gift-giving bonanza: "The first thing to notice is that Battlefield 2142 was the obvious winner this Christmas. While it still doesn’t have the popularity of games such as Half-life 1, Half-life 2 and even its older brother Battlefield 2, the holiday season has given it a second breath and the chance to revert what was a sharp drop in its number of online players." There are still more Battlefield 2 players, mind you.

Also fascinating - a graph on 'The Day Steam Stopped', showing the massive and obvious effects on Half-Life game playing for a storm-related outage, and a trends preview for 2007, which had a smart 'big question': "Will there be enough fans of online, vehicular-based mayhem to pay off the investment made by [Unreal Tournament 2007]’s and [Enemy Territory: Quake Wars]’ developers? Will they crush Battlefield, be crushed, or just split the player base? Hard to say by now, but should be an interesting thing to watch."