I have an app (Fast Friends -- originally Top Nine) with 125,000 users and absolutely no problems hosting -- I'm actually running two apps off the same server. I'm sure if I had won the user war against Slide I'd need a dedicated server ;)<p>Unless you have a media intensive application (ex: video, music, etc...), hosting isn't really <i>that</i> bad. I would venture to guess apps like "X Me" and "SuperPoke" would do with a single powerful dedicated server, since theres really not much going on. Also, Facebook hosts the images on any profile, so any bandwidth there is only needed until their proxy server picks up the image.
yeah, if hosting is a big problem for you, and you're legitimately optimized right, then email about anyone in the valley -- you can get a bridge loan (convertible note) for $20k - $50k in no time (less than 5 days). if you don't know anybody, email me. go to any investor and say "I need money because my site is growing too fast!" and you're solid. end result: hosting is not actually a problem (even though it looks like one), but making a popular app is much more of a problem.
This is a hard problem.<p>If your app isn't successful then there's nothing to worry about.<p>But what if your app is super successful? How would you ever be able to secure enough servers to meet the demand without burning a very deep hole in your pocket?<p>What we need is a Y-Combinator like incubator for Facebook Apps - a company which will host your app and help you scale it up for a chunk of equity.
If your site gets big, ask someone to host it for you (30boxes hosted one of the most popular apps). You can sell it to RockYou or Slide if it gets too popular. IMO, not a real concern, and when you reach this point, then you will think of some solution. <p>For now, worry about the real issue: "What is a problem that I can relate to and solve for Facebook users?"
My company loaned servers to one of the top 10 Facebook apps for a few weeks as their app grew to over 3.5MM users.<p>The hardware: Two modestly equipped boxes from ServerBeach.com -- and it ran super smooth.