I've been thinking about this question for the past six months as we have been eagerly awaiting the launch of the iPhone app store and with it, the iPhone app ecosystem. IPhone apps have been out there since the emergence of jailbreak but its clear the the launch of the app store legitamizes this market.

We've made one investment in the Facebook app ecosystem, Zynga, which is the largest network of gaming apps on Facebook and the other large US-focused social nets. And we've made one investment in the iPhone app ecosystem with Pinch Media which provides free analytics and an advertising system to monetize free iPhone apps.

So as we've watched Pinch launch its services to the iPhone developer market, I've been wondering what will be similar between these two ecosystems and what will be different?

At first blush, it seems that the iPhone has attracted a broader base of developers and at least to my eye, a number of more 'serious' (ie productivity/business apps). But it's also going to be true that gaming is likely to be the most popular category in both ecosystems. Just look at the app store right now and you'll see games all over the most popular lists.

On Facebook, Zynga and a few others developers have come to dominate the games category. Will it play out that way on the iPhone too?  Hard to say but its clear that we'll all be playing Super Monkey Ball on our iPhones the way we play Brickbreaker on our Blackberries.

The biggest question on my mind is how big will the first mover advantage be in the iPhone app ecosystem? On Facebook, the few who got their first, like Slide, RockYou, Zynga, iLike, Flixster, have come to dominate the ecosystem.

That has a lot to do with the rules of the game that existed when Facebook launched the app platform and how they've tightened them down since. And Facebook is a viral social system. Is the iPhone?  My gut says yes, but I am not sure its virality is as baked in right now as it will be over time.

If first mover means as much on the iPhone as it did on Facebook, then the early stars like Loopt/Yelp, Super Monkey, Twitterific, and others will have an advantage.

The design of the app store front page is also important. Will Apple favor paid apps where they get a cut over free aps where they don't? Right now, the front page looks pretty balanced between most popular, staff picks, recently popular, free/paid, etc. But it's certainly been true in the music store and the podcast page that being popular is self reinforcing and I suspect that will be true with iPhone apps as well.

I am sure some of the answers to these questions I've been asking are already known. And I am sure that all of you have been thinking of and asking the same questions. So comment away and educate all of us on this important question.

Read more of Fred Wilson on his blog.