Google have said that there is a list of offensive words that it will refuse to do the instant search with.
That is a huge problem that they need to fix immediately. The worst example that came out of the announcement was when Irina Slutsky, who was at the event, complained that when you search for her, until you press return the page is completely blank. It doesn't matter if you've typed her entire name, it still thinks you're searching for an offensive term. Hell, when you type "irina sl" you get a blank page. Now, you can still press enter and it'll give you the results, but what if people searching for her think they were on the wrong track and decide to search for something else?
There are other amusing instances of this, like you can type "i love" but "i hate" gives you no results.