It's not exactly what you'd expect, is it?

Firstly, it looks horrible. Just look at it. Secondly, it can create a range of issues, from duplicate content to potential tracking issues (if you have multiple URLs all being recorded and split up, instead of tracked as one page). In truth, it's very rare that any of that content will be completely different - it's almost always duplicate - but we wanted to see what would happen if the two pages served completely unique content.