Joi stepped on an interesting blog-related problem when he was preparing to migrate his blog to TypePad.  It is a common problem, but it took me by surprise too.  Duh.  The problem is, as I call it, not-really-permalinks.  When you change blogging service provider/software or domain, your permalinks no longer points to your old posts, causing links from all the posts that reference your posts to be broken.

While most engineers would reach for a solution by reflex, I am busy thinking about how effective it is as a barrier-to-entry.  Opposite side is just as important: how effective an incentive is zero hassle migration?  So far, my answer for personal blogs is "important only to a small fraction of the market", meaning it is a serious problem only for blogging elites.  For business blogs, my answer is "important but less important than price."

Note that marketing can inflate the seriousness of the problem or the solution.