Many of my favorite mobile apps are immobile. I can't take them with me.
At least not if I'm going somewhere that doesn't offer a fast internet connection. Like the small town I recently visited for five days.
I couldn't use Twitter there because it kept timing out before downloading the latest tweets. And Facebook was completely useless - it wouldn't even let me view stuff that had been previously downloaded.
Almost all the apps I use - including some games that shouldn't even need a connection - became immobile.
It reminded me of the early days of desktop development, when too many developers assumed that everyone had a computer as fast as theirs. These days too many developers assume that everyone has a connection as fast as theirs.
One of the most painful things we did when developing Glassboard was ban ourselves from Wi-Fi for a week. I live in an area where cell coverage is really spotty, and using our app without a fast connection was eye-opening and humbling. I spent the next week rewriting huge chunks of the app so it would better handle poor (or non-existent) network connectivity.
If you're a mobile developer, I urge you to do the same. Spend several days using your software without a fast connection, and chances are you'll find - as I did - that you've unwittingly built an immobile app.