12seconds.tv, which launched two years ago as a service for leaving 12 second-long video status updates (described as a ‘Twitter for video’), announced today that it plans to close up shop on October 22. The service plans to release a download tool for users to backup their videos later this week.

The shutdown is due of a multitude of causes. Co-founder Sol Lipman revealed to Mashable that traffic on the site has remained at the same level as it was two years ago, when the service first launched. The costs of maintaining a video-based service are steep, making it hard to justify continuing a service through lean years.

One of the major reasons behind the shutdown, however, seems to be Twitter’s narrowing down of its app ecosystem, which prohibited the startup from propelling ahead. While Twitter has had partnerships with many of its ecosystem developers, specifically with the launch of the new version of its site (many photo and video-sharing sites, for example, for their embedded content), a number of players — including 12seconds — have been left out of the action.

Partnerships with Twitter — and even many of its apps on mobile devices — help services building on the platform to find new markets and audiences. But as this ecosystem tightens and leaves certain players and up-and-comers on the sidelines, Lipman sees the opportunity for developers to build on the platform shrinking.

“I don’t really see the growth in Twitter that we were seeing. I don’t see it as an explosive growth opportunity right now for a third-party application builder. In any ecosystem, eventually there are going to be winners and losers. I think that’s going to shake out more and more as time goes by,” Lipman told Mashable.

On the bright side, two of the co-founders of 12seconds.tv have found jobs at AOL, and another at eBay, where the team will hopefully continue to work on bigger and better future endeavors.