Should bower_components be gitignored?

The official Bower page stated:

N.B. If you aren't authoring a package that is intended to be consumed by others (e.g., you're building a web app), you should always check installed packages into source control.

Make sure to check out the link in the quote, it discusses some pro and cons. The main pro it mentions is that checking them in ensures that your dependencies are always available, as long as your repository is available. No matter what happens to Bower, GitHub or whatever else would be needed otherwise.

The .gitignore file in a newly generated Yeoman AngularJS project has bower_components (and node_modules) listed to be ignored (if you don't know Yeoman it is a very reputable web scaffolding tool for modern webapps, so that's good enough for me!):

.gitignore

node_modulesdist.tmp.sass-cachebower_components

There's a time & a place for both approaches. For Yeoman it's appropriate to rely on bower.json because it's a tool in a toolchain and needs to stay living and breathing with the bower ecosystem. For a deployable web app, it's generally good practice to commit dependencies and maintain more control.

Here's an good article I like that discusses this.