It's pretty clear they're using this as a hook to attract gamers who are into the BF/CoD type games and might not have played the previous two ME instalments. Which is fine in my books, I mean that's what a demo should do, no?
For me personally...well I was never going to buy BF3 and even if I was I don't want to play the ME3 demo. I intend to stay as spoiler free as possible till launch. After what happened with DA2 I may even wait a few weeks till the inevitable launch bugs are patched.
What's actually funny is that I had a skim of the thread over on the official Bioware forums and they're all bitching and moaning at the unfairness of it all (I know right? Shocker!) I mean it's a demo for goodness sake! It's not meant for the fans who are going to buy the game regardless, it's for people that might not have otherwise been interested.
On top of all that, (because there's no way save importing would be included) why would I want to play a demo with the default Shepard anyway? That guy is an imposter!