If you working on an Internet startup and you're not thinking about SEO from day one: you suck.
Any decent marketing strategy is at least going to give a nod to SEO. Is your team is so consumed by your awesome product that you think it's more important than marketing and distribution?
I really hope that isn't true of anyone here. If championing product over marketing and distribution does sound like your team, I have GOOD NEWS! — you'll be too busy jerking each other off to notice that you're not making any money.