I'm pretty sure they were all the rage when _I_ was at school, but that was long before the iPhone.
I'm curious on what grounds they blocked the app.
Mentioned below in a few comments but it was on the grounds of using his name/likeness.
(Not the parent poster) I found out about them in 2008-2009, and they were quite popular online and offline.
If you're curious, maybe you can look into Chuck's lawsuit against Penguin's book of Chuck Norris facts. He would eventually "co-author" his own book. The obvious guess here is trademark infringement (over use of Chuck's name/likeness) and/or copyright (if some of these facts were lifted from his book).
> I'm curious on what grounds they blocked the app.
The app probably used his pictures or his name, which are easy candidates for copyright or trademark-claims.