3 sec Upvote Rule

Recently I noticed a wait 3 sec between upvotes, and while I have absolutely no problem with it; I didn't know if this was a recent addition or an old one that I just didn't notice because I never upvoted that quickly. Is Steemit getting used more? Are they having to try to restrict bandwidth? How many users are the current servers suppose to be able to support? All interesting questions as Steemit grows.