Personally, I think Steam Achievements are quite enough for the ego boost.
I'm just not one for K/D ratios, wins, etc. At least not for games being played for the fun of it. Its not something I can put my finger on, but to me it seems that
published stats steer people toward "playing for the stats" and not for the team or for the fun. And there will always be the debate of which stats should be kept, which should be shown and/or which are more important or meaningful. Now, if a tournament wants to keep stats for the tourney, or if third party databases or individual servers want to keep stats (like we did in early CoD or MoH), that would be fine with me.
As I don't care about stats per se, if they're added I really wouldn't care as I don't think I'd ever look at them. But I'd just hate to see the fun of a team accomplishing a victory over an oppenent tainted by quests for stats.
And then there are the stat hackers or exploiters.
And weren't some of the early server problems with AA3 (and BFBC2?) from in-game updates to a database server?
The logistiics of keeping stats would have to be considered, too. I'm sure its not something you just code in. There's a good deal more involved.
Stats just seem to be a whole lot of trouble for such little benefit.
I'd also like to see the total death toll of the "online" war. Lets see how long it takes to surpass the real war =P
I agree that a running tally of the body count for each side would be interesting indeed.