Perhaps it goes without saying, but the story of TechCrunch is a long and complicated one. Even in its earliest days, there are some details that are a bit fuzzy and often go overlooked…like that it had two founders right off the bat. Though it was almost immediately framed as being Mike’s blog, Mike Arrington had found a business partner in Keith Teare (who actually admits to having advised Mike not to do it.)

Today at SXSW, Keith Teare previewed his next project: Just.me. With over $2.5m in funding raised, it’s a mobile-only social network built around fine-grain control over who sees your content — even if that means that you’re the only one.

While I call it a “social network” above, that may be a bit of a misnomer. It really seems to be more of a hybrid of three ideas: a private journal, a messaging platform, and a social networking tool. Perhaps it’s easier to just explain how it works and let you define it for yourself.

Just.me focuses around the idea of “messages,” which are user-created bundles of content. Each message can be made up of any number of photos, videos, of voice items. By default, messages are saved for your eyes only, which is where the “journaling” bit above (and Just.me’s name, for that matter) comes in.

You can also opt to share each message with a group of friends, with each friend being a contact straight from your address book. Just.me also auto-builds groups for quick sharing to your most frequent contacts, for those who’ve checked in near you recently, or for those you’ve included in groups recently. Thus, it’s part messaging platform.

Finally, you can share a message with the world. Do that, and you’ll also be able to post your message as a publicly viewable link to Twitter, Facebook, and (eventually) Google+.

Now, for the big question: How do they make money?

It’s actually quite clever. If a user adds a brand (whether it’s a major company or local business) to their Just.me address book, said brand can privately send those users special offers. And if the brand’s offers suck or they get too spammy? The user simply nixes them from their address book. Brands can also send messages to the public stream on a price-per-view model.

Just.me’s most direct competitor (besides the mammoth social networks with which everything inherently competes) is probably Path, which has quite the lead in hype, time on the market, and funds raised. While Path doesn’t specifically focus on private journaling, it does allow you to mark an item as one to “Keep to myself.”

Just.me raised a $550k seed round last summer from True Ventures, CrunchFund, Google Ventures, Ron Conway, and Beta Works. This past January, they raised a $2.2m Series A led by Vinod Khosla and backed by True Ventures. Just.me will launch later this year, and is currently in a super-limited Beta stage.