Google quietly took away the + search operator. From the Wired article:
On Wednesday, Google retired a longer-standing “plus”: the + operator, a standard bit of syntax used to force words and phrases to appear in search results. The operator was part of Google since its launch in 1997 and built into every search engine since.
Unlike their other recent closures, the removal of + was made without any public announcement. It could only be found by doing a search, which advised the user to double-quote the string from now on, making “searches” look like “awkward” “Zagat” “reviews.”
Read the Wired article: Google Kills Its Other Plus, and How to Bring It Back.