Betaworks, the company behind Bit.ly, news.me, Chartbeat, and now Digg, has added Instapaper to is portfolio.

Instapaper has served as a nice complement to news readers like Google Reader (or whatever you’re using these days). It’s great for when you find things you want to read later that you didn’t actually get to through your reader, and don’t have easy access to the star feature. With Digg building a Google Reader replacement of its own, it will be interesting to see if Instapaper plays a role.

Of course some current alternatives to Google Reader basically render Instapaper unnecessary. Feedly, for example, offers its version of the Google Reader starring for any page you visit on the web, and adds it to your reader. Still, the addition of Instapaper could be a key element of Digg’s creation. Either way, people already known and like Instapaper, and it will continue to have its own user base.

John Borthwick told TechCrunch in an email that Instapaper will be a “perfect fit with Digg and its forthcoming reader.

Instapaper creator Marco Arment discusses the situation in a blog post:

When I launched Instapaper in 2008, it was a very basic web app. It quickly expanded to define the pillars of the read-later market: a one-click “read later” bookmarklet, a web sync service, an adjustable text view optimized for reading, and an iPhone app with offline saving. I did almost everything myself, which worked well for the first few years, but for the past year, I’ve had a lot of trouble keeping up with it.

Instapaper is much bigger today than I could have predicted in 2008, and it has simply grown far beyond what one person can do. To really shine, it needs a full-time staff of at least a few people. But I wouldn’t be very good at hiring and leading a staff, and after more than five years, I’d like an opportunity to try other apps and creative projects. Instapaper needs a new home where it can be staffed and grown, but I didn’t want to give it to a big company that would probably just shut it down in six months.

Being familiar with Betaworks (apparently eating lunch at their office a lot), Arment figured they’d be the right company to acquire a majority stake in Instapaper. Betaworks evidently agreed.

According to Arment, the deal is structured so that Instapaper will remain a top priority, and he will continue to advise the project indefinitely.