Hashtags - the wonderful concept that allows people to create their own controlled vocabulary to emphasis what they want to say or to refer to a general concept (usually on Twitter) is now going to be embraced by Google search. However, as with all things Google - there's a catch. They're only going to show up if the hashtag has been used in Google+ rather than something like Twitter. The idea is fairly obvious - results will appear, you'll click on them and lo and behold you'll end up looking through content at G+ rather than Twitter, Facebook or anywhere else.
It's going to look like this:
I had to borrow the screenshot from a very good Makeuseof article on the subject because it's a US option only at the moment.
Quite frankly, it's a shame. Google is continually trying to force its hand over search, and far from getting 'everything' - we're being limited more and more to just what Google thinks we should see - and that's always only going to be for their benefit, not the searchers. Just remember folks - Google is not your friend.