I have always found that whatever IDE I'm using ( Eclipse, Visual Studio, Aptanna etc..) line numbers always seem to be off by default. Not having line numbers makes it difficult to debug and if you're going to be coding you are definitely going to be debugging. Do the majority of people not use line numbers?
Intellij makes line numbers mostly unnecessary. Click on the link in the stack frame displayed by the debugger and you go to the right line in the right file. And if you really must know the line number, it's in the bottom status bar, about 3/4 of the way over.
That's a nice way to handle things, I've never tried Intellij maybe I will for my next project. Still if you have to look at log files for why your program crashed, line numbers are almost essential. Just a small gripe of mine that I never understood why it's done this way, maybe an IDE developer will see this and chime in.
I use the "jump to line" command when I'm looking up the cause of a compiler error message, but in an IDE world I doubt I'd need even that, since it'd presumably just link the errors to the appropriate lines visually.
I think line numbers help in gauging how large a class or method is if the file is longer than a few hundred lines. They also help organize things for me, if I roughly know what line a certain piece of code exists at I can usually find it faster (using jump to line) than without having line numbers.