In a new interview with Bloomberg, Twitter CEO Dick Costolo hints that the ubiquitous public-conversation venue will offer something akin to Facebook's private group chat function, and an in-between "Whisper Mode" option for taking public conversations private. So, yes, another step in the steady march of Twitter becoming just a quirkier Facebook.

Costolo begins the interview making the case for the idea that Twitter is "already mainstream," countering recent press that has been repeating the notion that Twitter is too weird, chaotic, and difficult to use to ever have the real broad appeal of Facebook. Basically he argues that you now see scrolling tweets under nearly every newscast and pseudo-newscast on TV, therefore Twitter is "everywhere," not just on a website.

Then he gets into the topic of the Direct Messaging function and how they're going to launch this new in-between thing.

So when I talk about direct messaging within the Twitter application and the work we’ll do improve it, what I’m talking about is there are frequently public conversations on Twitter, and Twitter is entirely public conversation. It’s real time, what’s happening right now, public and conversational.

There are frequently public conversations that you would like to grab hold of and take into whisper mode with a friend and say, hey, this thing has happened. Look what these people are talking about. What do you think about this, with a friend or more than one friend. So being able to move fluidly between that public conversation and the private conversation is something we’ll make simpler.

So, yes, that sounds like two things, or maybe it's just the creation of something that's like Facebook Messenger (so that all the starfuckers tweeting at Kim Kardashian can be like, "@KimKardashian let's take this into #whispermode," and then she can be all, "no").

Also, it definitely sounds like Twitter is feeling the heat from investors to keep growing at a stronger pace. Turning a profit might be nice, too.