Well, there are certainly a lot of "what ifs" that go into this. Those are what make it really difficult. What if someone sets up a local server and tries to make falsified records? Do I limit it to just public servers? What if the admins can't be trusted? Knowing the immaturity in gaming communities these days, "what if's" are really, "What happens when?"
I would have to set up some kind of encryption so people don't manually try to add statistics to the web script. No guarantee that can't be cracked.
Some other areas of concern would be:
Cross-platform network coding. Not a huge deal; I just don't know how to do it yet.
Storing the statistics. Keeping statistics as detailed as I want could lead to really large files. Hopefully it won't get too out of hand, but the space necessary for the "who killed who" statistics will increase exponentially as the number of players increases.
Funnames, clan tags, etc. While I think it would be good to force people to stick with one name (I hate it when people have to change names every half hour), things like colors, extended characters, and the like would not work well on the web page. I was thinking of having some kind of translation thing which would translate extended characters to the closest printable characters and remove formatting. For clan tags, I was thinking it would be cool to have official clan setups where you'd have to be logged in and be a registered member of a specific clan to use its tag, then you could use the name with or without the tag.
It might be possible to make matches completely automated. If a clan leaders log in and execute some sort of start match command (maybe using 3 map names as parameters), the server gives them login and sets a password. After the match takes place, the server uploads the winner and stats to the web database.
Then we could have clan rankings similar to those of the player rankings. Make matches and clans actually have a meaning, because you would be ranked based on which clans you play, and people won't be able to create and disband clans every other day.
Hmm, another thing that might help the community is to have some sort of player voting system, so if players act up, you can vote against them for poor conduct. You could vote in favor of players as well, if you think they're a good sport (or maybe just plain good). Maybe have a "most popular" category.
This would be more for admins, though. If players have really bad ratings, it might be a sign that they need to be banned.