Today I published a post on SP365 which attempts to explain host-named site collections to the uninitiated in the form of a 

Host-named site collections are a key part of SharePoint 2010’s multi tenant support and offer a huge amount of scalability. They provide support for multiple root named URLs (vanity URLs) and in many cases are a valid alternative to creating additional Web applications.

If you have any feedback or suggestions, feel free to add a comment.