While most Web 2.0 startups and virtual world darlings are taking venture capital we've taken a different path by working with idea that we will fund our growth by providing products and services which people will find so valuable that they will actually pay to use them. It's crazy and old fashioned, I know.
I won't go into the many ways in which a shorter runway keeps us focused on our users and their needs but instead I'll just mention that when we're elbow deep in the details of billing I understand why lots of startups just go for eyeballs: it's hard to be both nice and paid.
For example, there is an easy way to bill you for Tomorrow Space event halls. They're daily rentals so it would be easy as pie to charge you at the time you make a reservation. But life is more complex, and you'll want to change and cancel reservations, and sometimes you'll forget that you even made them and nobody will use the hall. So we added a bit of code which only records a rental fee the first time a guest arrives at your event. You can poke and prod event halls all day and only pay when you're actually hosting an event.
It's not that these small tweaks are individually hard but to make this system something you feel good about supporting we're doing quite a bit more work than just plugging in a Paypal shopping cart and calling it a day.
Now there are edge cases to find and test cases to write, so it's back to the code mines with me.