I am looking to make an iPhone / Android app for my university using the Appcelerator Titanium framework. The app will rely heavily on a server backend which will pull information from other sites, figuring out what is relevant to the user then deliver the content.

Some of the information is individual to the user (calendar data), other bits are updates frequently but are shared (bus timetables) and others are static and the same for everyone (magazine articles).

I was going to use django as I am fairly proficent in python so I thought it would save time.

My question is, which hosting services do you recommend to host the server backend? I am expecting about 9000 people to use the app with very random spikes in traffic, but unfortunately I have very little to go on at this stage.

I have heard a lot about Webfaction, is it suitable for something like this or am I likely to need something bigger? I don't really want to fork out for a VPS at this stage. What about Amazons EC2? Would that be more suitable than Webfaction?

Sorry for the fairly open ended question, Im sort of new to this so I open to all suggestions.