SymbianOS has a DRM called "SymbianSigned" that can prevent you from installing and running software on your own phone without permission from your carrier. This excellent article explains the danger from this:
Now, please don't stop reading just because you're not a developer. This all affects you because it will affect the software you can load onto your shining new smartphone. One of THE strengths of the Symbian scene, even if it's not often recognised as such, is the community involvement in software development. Applications are used by enthusiasts, feedback given and improvements made, on an ongoing basis. Among other things, Symbian Signed implies that applications are more complete at birth, as developers try to avoid the feedback and improvement cycle because of the cost implications. But without that cycle, applications are less capable and usually buggier.
(Thanks, Ewan!)
