Google has replaced the + (plus) operator for their search. While looking for a certain expression (using the plus operator) Google tells that from now an double quotation marks are necessary to find an exact expression.
Not sure if I like this, however, it looks like there are not many options to ignore this change. This probably has to do with all the G+ notation. It feels to me as bad as product and event names like .net or build which in combination with the new double quotation mark operator find some 2,490,000,000 results not relevant at all.