That's a very good point. What's the best way to get across to a interviewer that you would love to work on outside projects, but simply were not allowed to?
I've been at a company that discouraged blogging, so this does happen.
"What's the best way to get across to a interviewer...?"
Just tell them. I wouldn't stress too much about it. If the person hiring you doesn't realize that there are tons of good programmers out there who don't blog, then you may not want to be working for them (i.e., they're newbies).
