Mash-ups will be big. Yet, as Dion Hinchcliffe points out , the number of mash-ups released per day may not be huge today (three per day, according to the data on ProgrammableWeb ). But they will be on the increase, and the more APIs there are available...
This is the kind of stuff that makes YouTube great. Thanks to Tommy for the pointer.
In case you ever wanted to know what the inside of a mouseball looks like.. ...you can watch this .