Why does ask.com make you wait 30 minutes when you comment to much?
I think to make sure your not a spammer. :p
To tame the trolls.
It's to make sure you're not spamming. You can still ask and answer questions though.
To prevent others from spamming up this site.
Just to keep you from spamming, even if you don't it keeps those who do at bay. It's quite a nuisance when you get into a good conversation.