Including a license is the #1 reason myself and many other people stray away from code on the internet. I won't touch a project if it's not stated properly.
And to be clear, just writing that your project is MIT licensed or sticking it in a package.json or making a small remark in your README doesn't cut it. You need to follow the terms of the license you wish to use (my comment on the matter: http://blog.nig.gl/post/48848761220/just-saying-something-is...)
(always a good read: http://www.codinghorror.com/blog/2007/04/pick-a-license-any-...)