There's a difference between pointing out a company that doesn't have a clear advantage and saying that given an idea, it's one worth investing months of effort in despite the fact that it doesn't have one. You need to remember that most ideas you execute on generally fail (and take time in the process of failing,) so you need to be chooosy when it comes time to dedicate yourself to one.
That said, being first is a small advantage, particularly in a new space, but not a great one. The real benefit of being first is making it possible for you to build a bigger one (like mindshare,) but there's a lot more luck involved than if you had just started out on a project where you had an incredibly larger advantage. You don't see the failed versions of Moo, now do you?
Look at Moo. They are A) profitable, B) run off Flickr, C) in a replicable space (e.g. not hard to copy), and D) still winning.
They win because they were first, and because they are cooler than the others.