Why are l4d maps showing up?
This is a good question. I've not changed ANYTHING in the master server query code, but I cache the master list and recycle it a lot since hl2master is about as reliable as a scout slowly walking toward you from the other base
I suspect it's one of two things:
1) People have switched their tf2 servers to l4d, but they're still on my tf2 master list
2) something broke in the update
I'll add some logic in to filter out the first case.
Update: Ok, It turns out I'm pants-on-head retarded and can't write averaging algorithms to save my life. player count bug should be fixed now. Also, l4d and CS maps no longer show up. Hooray progress.
You can probably increase the polling time to 25 minutes or so. Most servers have at least a 30 minute rotation so every 15 is a little often.
Some servers run customs on a shorter cycle. I know the server I admin sets a lot of our customs to 20 minutes because while we enjoy them, they tend to empty the server. I imagine other admins are more aggressive on this. Also, at this point, there's no additional database overhead for running too fast; so it's moot.
Update 2:
This only searches servers currently running the map though, not historic results. The reasoning here is that doing a partial match on that massive db is more than a little slow.
Try this:
http://fireslash.net/~fireslash/tf2/in_rotation.php
Still experimental, but it should let you locate any server that has run your map (since the time I accidently cleared everything like an hour ago). It'll tell you what server, what map version (hooray wildcards, use %), and what time the map was last spotted.
Update 3:
So, the map list is getting pretty insane, so I'm only going to display maps with an average player count greater than 1. you can still search for lower rated maps, they just won't show on the stats page.