Ask YC: How to handle fast user intake

Although not applicable to me (one day!)...

If a pet project suddenly becomes popular and expands beyond it's indended users (bandwidth, resources) how would you handle it?

You need to move to a dedicated server, rewrite a portion, and somehow find the time and money (its a side project - you have a day job).

Also if it's a novel concept but not groundbreaking, how do you keep your user base when it's easy for someone else to capitilise your idea?

What are the options? Has this happened to anyone here?