I'm going to side with Cass on the whole "multiple villains is a bad idea" issue. It's unnecessary, and it hampers the story because that's one more character you have to explain and integrate into the story. My big hope is that Venom is just being set-up for a Spider-Man 4.
There does seem to be a lot going on storywise in the trailer, but it all seems to tie together in the whole "Dark Spidey" idea. Again, I dig the darkness of it, and exploring how power corrupts seems a natural progression of theme for he character.
Raimi's got my nine bucks if he makes one of the villains is a one-armed monkey. I'm addicted to the brand. Shameful, but true.
Oh, and my wife thought the trailer was confusing and pretentious, and when I explained the Venom/symbiote concept to her, she replied, "That's really gay."