A lot of buzz about mashups is pretty compelling but at the end of the day I get more of a kick out of the mashupisms I have discovered.
1) My personal favorite is show me a good mashup that does not have a map. It's pretty hard to do if you think about it. Every mashup example that is used has some sort of mapping - geo visualization thing to it.
2) If mashups are so cool then why when you Google mashup you get more music mashups than the development kind. That to me thats more coincidence than anything.
But when you get right down to it mashups in a business setting are the equivalent to a spreadsheet vs the old mainframe reports. The value for both is that the power goes to the user. Mind you a smart user.
I interned at a place (a gas company) that was hardcore about mainframe reports. Every day or week people used to walk up to IT and they had these lockers (much like a bus station) and they would enter a code and thier door would pop open to a locker with a report. Some of these reports required a cart to carry the greybar paper.
However the super smarties with friends in IT would just get the dump and pile it into Excel and then manipulate it, graph it filter it whatever. It impressed their bosses since they had pie charts or summary tables and also saved them from having to carry these giant books about. One of those smarties was my mom.
So, the value is there but just remember the value is not the cool or pretty. The value is the person who can react to data based upon their metrics without having to run to the lockers so to speak.