What Matt Homann has called the new starving artist syndrome. That is, explaining to your spouse, boss and others that blogging is a great thing when you cannot point specifically to cash that comes in because of the blog.
Writing good posts on a regular, even daily, basis is also much, much harder than people think, even for people who are writers by nature, especially over a long period of time.
By the way, as Ernie the Attorney noted the other day, explaining to people what a blog is hasn’t gotten any easier over the years either.