From the 'wow! I didn't see that one coming' files:

Symbian has always been the big fish in the mobile operating systems pond. It has always been the 'big scary proprietary vendor' that Linux has been targeted against. That all changes today though as Nokia has bought out Symbian and announced that it is making Symbian into an open source effort.

WOW.

Talk about a completely game changing monumental turn of events. The Symbian ecosystem will now have little to no incentive to move over to Linux (and even less to Windows CE). Linux will continue to be championed by Motorola and it's personal fiefdom at that LiMO foundation, and the mobile market is now a battle between TWO open source mobile operating systems.

Strategically this move makes a tonne of sense.

Nokia owns Trolltech (developers of Qt and Qtopia) and with Symbian open source there may an opportunity to mix and match Qt with Symbian code to end up with some massive superset of mobile open source capabilities. For strategic reasons, Nokia was not likely to ever fully embrace Linux due to the undue influence of Motorola in mobile Linux.

In a larger context Nokia's move is perhaps a realization that the proprietary vs open source debate is one that proprietary vendors can no longer win.