You hope your app will be a hit. (If not, then quit writing it and choose something else.) If it’s a hit on iOS, it could be a hit on Android too — and you can bet that customers will ask for a web app version.
You don’t want to limit the success of your app just because you didn’t want to write your own server.
Android and the web are very much real and have humongous user bases. Additionally, the app eco system will soon hit this factor - which is that it is much harder to get your userbase to move along with the pace of development of your app. And then Brent goes on to a much more important point.
Everything has gotten easier and cheaper. These days you’d run services on Amazon, Azure, Engine Yard, or Heroku. Or get a virtual server on Linode. You’d choose from one of the many excellent systems like Ruby on Rails, Sinatra, Node.js, and Django. You’d deploy via git or Mercurial.
If you can learn Cocoa, you can learn this stuff. (And so much of it is wonderful — you’ll enjoy learning it.)
I have been toying with Ruby on Rails for the past couple weeks and I must say that in 2 weeks, I am more comfortable developing web apps with so much limited experience than ever. I <3 it.