recent job postings insinuated that this feature would come around sooner or later -- it makes perfect sense for it to be included as part of the Google+ experience to help strengthen Mountain View's bid against the likes of Facebook.
Also on the company's white board is Questions, a likely love child of Google's $50 million acquisition of Aardvark. When the source code offers up hints like "you might try rephrasing or tagging your question to make it easier for someone to answer," along with the utterance of sharing questions with others and commenting on answers, nothing could be more indicative of a social service. There still isn't a strong indication that we'll see these two features pop up anytime soon, but the hamster wheels are definitely turning right now, and we're piecing the clues together. At the rate things are going, these services may easily be ready before we all get invites.