Another school of thought on this is if you're trying to look bigger than you are, which alot of startups do, "we" might be more appropriate.
I've seen this a lot in hobby industries - guys working out of a tiny rented space in a office park find themselves wondering why their customers think they're a big company with a lot of money. This is inevitably due to their trying to look "professional", which tends to be a mingling of actual professionalism and aping the promotional styles of larger companies.