Apps Don't Last
From Daring Fireball, the eulogies for apps (Dropbox-acquired apps, in this case) that are no longer with us, including Mailbox and Carousel. And of course, we can’t forget some of the many other apps that have been acquired and retired, or the ones that have faded away and died.
This is not to say that you should not buy apps, but investing in something that is software or a web-based service should cause you to think a little. I previously wrote about paying for software and impermanence, and I think this is all related. You need a fallback plan.