You guys are right, there are use cases that a shared certificate might not be as bad as I made it sound. But I hope people really understand the reasoning behind it first.
In Ed's example I would seriously consider a wildcard SSL certificate if the business wanted to have multiple host names for their products.
In Brian's example I could see where the family might not be that serious about using SSL to project confidence to their end users.
Overall though, I think having the option will promote more bad practice then it is worth. Afterall, if someone wants to share an SSL certificate there are other things to consider than just getting to a specific url when SSL is enabled. (i.e. the auth cookie on login will not work as you try to switch between domains).