Your Startup Needs a Website (even if your product isn't ready yet)
rocketwatcher.com
rocketwatcher.com
Still, once a startup is reasonably sure that they're sticking with their plan, no reason not to get one out there ASAP.
I'm doing this with a placeholder site at http://codeboff.in/ and a blog that drives traffic to the site (and private beta list) at http://blog.codeboff.in/
(I hope sharing these links will not be treated as spamming in the context of this discussion)
I went with the more time-consuming blogging approach instead of the traditional and quick advertising pilot because I'm bootstrapping this from India and web ads are more expensive to me by 6x to 8x (or whatever the purchasing parity difference is) and I can't justify that expense, especially in the light of my previous startup ideas which in retrospect have been more or less cuckoo.
I agree that startups do pivot before launch. I think you have to agree to take that risk against the market research advantage you're getting. It might help to keep the blurb on the sales website on the vague side to absorb minor pivoting.
edit: Spun off in the middle. What I was trying to say was that interest in the blog justifies the much greater investment in engineering that's going into my startup.
Without that interest, making up my mind about the idea would have been pointless.