Based on the job posts on SO it is. But it's decreasing in popularity quite strongly comparing to Cassandra for example.
http://www.reallyhyped.com/?keywords=cassandra%2Credis%2Cmon...
Joking aside, SQLite is on a ton of devices, yes. But that's primarily because it ships with OS's and is in lots of embedded devices. For web development and other server-side things, I get the feeling that SQLite is not as heavily used as client-server databases.