I don't know about hacking but I recently started playing it again and there's still thousands of servers to play on. I believe COD4 to be about as big as Counter-Strike now and it's the most played game at my local PC LAN Center. If you have the money I'd recommend picking this up as well as MW2 when it's released.
I think the COD4 community has matured quite well. A lot of servers set their own rules such as no Marty and no n00b tube, and almost everyone abides by them. There are still thousands of servers and hundreds are constantly full at all time.
Thanks for the info mang... I do rarely see a kill from the "tube" nowadays... unless they are trying for some challenge XP... or if they use the G36 (whatever the single shot one is)
Last time I played a month or so ago, it seemed that things have calmed down with hackers and assholes mic spamming. However, there were a few and occasional times when people spewed so much profanity that i left. Luckily, I enjoyed more so than when I first got the game when it came out.