For the second time in the last couple of weeks, my iPhone checkins are not working. I am a huge fan of the product. The market is huge, you are the first to the party, and there are so many ways to make money with this. But, if this keeps happening, you will lose users to the big guys ready to pounce and the startups with a better mousetrap. Invest in performance profiling and infrastructure or it won’t be pretty, or worth much.