I disagree in regards to Flash 10.1 mobile. Plays all sites fine with no lag and games play smooth too. As far as being vulnerable, any app that accesses your hardware in any manner can be a risk and exploited in some way.
Do you actually have Flash 10.1? Rocks on Android 2.2 and far better than I expected. If you go by the version on the N900, I would agree with your points on resources and also performance. Flash 9 on N900 and Flash 10.1 on Incredible or Droid 2 is like night and day. Heck, Flash Lite 4 on the Incredible with 2.1 OS blew Flash 9 on the N900 away. added: BTW, people stating similar media content on html5 is more efficient than Flash 10.1 final are probably people that have html5 as a vested interest to state such. They are both similar in their resource utilization, but Steve Hand Jobs is pushing html5 for less than "honest" reasons.