Why rate-limit searches?
I got the following error message on Super User:
You can only perform 6 searches within a 60 second window, please wait a moment and try again.
It should be fairly obvious that I'm a legitimate user (reputation 241), not a scraper or a DDOS bot.
If you improve the search so that it's not as awful as it currently is, then maybe 6 searches in a 60 second window ought to be enough for anybody, but as it is, please at least double the permitted searches.