Web based storage for apps

I was just thinking that there could be 1000's of great apps in development but the iphone will only be able to store a limited number .

As there is no hard disk how much memory would a typical app take and how many do people think could be downloaded before the phones memory was used up?

If you downloded too many would the iphone slow down to be unuseable?

Could apple use web based storage to hold all the apps you want but can't store on your own phone. So you could switch different apps from the web disk like a juke box.

Also any word of an office type suite with web storage (like google docs) They would have to have a wordprocessor to get taken seriously, surely.