[atlacatl]

The first thing that you should know and accept is that there are probably 10 other people working on the same application you have in mind or are working on.

Second, if you go the facebook route, the first app of its kind will likely be more successful--that incumbency thing. If it's a compeling app, hurry app and deploy it.

Finally, if you decide to create the website first, then your target market has to be well defined, i.e., you have a niche solution to a specific problem for a specific group of people. If it's too broad, creating the website first will not likely generate enough traction, unless you can create enough volume.