The sad fact is that RIM just can't seem to decide where it's going as a company. They have an entire host of phones that are totally obsolete[1], their tablet doesn't run an operating system that was built in house[2] and for some reason they decided to force people to have a blackberry phone to get the very features most people would use the tablet for.[3] So if I'm in the market for a phone, why on earth would I go with a blackberry?(And no, BBM is not enough)
Rather than build the OS themselves, they decided to acquire it. That tells me that RIM is suffering from a lack of creativity and while you can buy your way to innovation(Microsoft has been doing it for more than 20 years) it's always better to develop new technology in house. The fact that RIM didn't for a flagship product is a huge red flag.
When it became clear to Apple that they would need a new OS, they bought NeXT in 1996, and the OS they got that way seems to have worked well for them -- on computers and on phones. Also, Google got its mobile OS by buying Android, Inc, in 2005.
[1]http://www.engadget.com/2011/05/02/rim-announces-blackberry-...
[2]http://www.engadget.com/2010/09/27/rim-introduces-playbook-t...
[3]http://www.intomobile.com/2011/01/10/blackberry-playbook-tab...