[quote="alee":1do66z2i]Why would it hammer the server? Bandwidth wise, or CPU wise?[/quote:1do66z2i]
bandwidth, imagine 1 message user->server and 1 message server<-user per second (about one fourth to half the speed WoW does communicate with blizzard's server) per user.
let us assume, the user is playing about two hours a day. let us also assume, there are 500 users. let's assume a standard message sent to server is something like "hi!i'm at x800x600facing90attacking polar bear" = 46 bytes, for easier counting, 64b (send some variables maybe?). finally let's assume, the message from server is something like this: "ok, you attack a polar bear for 48hp, other players around you: otherplayer1/x810y615\otherplayer2/x820y625" = 107 bytes with only 2 players around, so we can round it to 128 without worries. so, 192b per second per user. 192*60s*60m*2h/1024=1350kB per day per user. 1350*500/1024 users = 659mB per day! this assuming, the 500 players plays for two hours daily.
the database is a second thing, imagine 500 queries per second
hope I saved hours of constructing before someone hot on "i'm making mmo" realized the above. sad. but true. but I'd love to see what you've done when you're done, good luck!