Mobile app-maker Seesmic on Monday told its customers that it would stop developing its BlackBerry app as of June 30, 2011.

[ad#Google Adsense 300×250 in story]In a note on its Web site, Seesmic said they were discontinuing “support for Blackberry in order to focus development efforts on our most popular mobile platforms: Android, iOS and Windows Phone 7.”

They also encouraged BlackBerry users to try out Seesmic on one of the other platforms.

With the problems that RIM has been going through over the past six months, you have to wonder if Seesmic is the first of many developers that will leave RIM behind. App developers have to balance the amount of resources it takes to build an app with the amount of money it will make from it.

With slowing sales of BlackBerry devices and already slow sales of the PlayBook, RIM is not showing developers that they have a platform for the future.