When there is zero friction to adding content to a notebook, the notebook will become a junk pile.
Very true. That's why I've never gotten into Evernote. I give it a go a couple of times a year because everybody keeps raving about it, but it's so easy to dump everything that seems even remotely interesting into it that after a week it's just an unmanageable amount of stuff that I know I'm never going to actually go through.
I think a little friction in your note taking apps is a good thing. It forces you to only store what's meaningful.
UPDATE (Jan 2014): A few months after I posted this I purchased Brett Kelly's Evernote Essentials ebook and it changed the way I think about Evernote. I now use it extensively in conjunction with OmniFocus.