Web 2.0 is fueled by data. Mashups don't mashup technologies, they mash together information. The more data you have, the more interesting the applications can be.
Unfortunately, we are suffering a data crisis. To be honest, there really isn't much data out there that is open that is useful to the average person, and I think that's why some Web 2.0 applications are having trouble getting traction in the mainstream.
There are still too many closed pools of data out there, and opening them up would make for some interesting new services.
Here's my The Top 10 Data Pools That Need to Be Open
1) Medical records - There's really just no excuse for this. Its my body. Any information that any doctor gets off of it should be owned by me and accessable online. I should be able to chart my cholestorol levels, weight, etc, going back to when I was born.
2) Credit card purchase history - Three months? This is silly. Not only should credit cards have my total history available to me online, but there should be APIs on it, too, so that financial data services can help me analyze my spending. I wouldn't mind if they did item level breakdowns or started pumping in SKUs, too, so I can reorder things, but that's probably just a pipe dream. Still, I think retailers would benefit a lot from giving the CC companies more data on each purchase. This also solves the Amazon purchase history problem as well.
3) Elias Sports Bureau - Why is there no consumer version of this? If I want to look up Frank Tanana's home record on Wednesdays, I should be able to do that in an ad supported site.
4) Public transportation - If I leave now, am I going to catch the R train or just miss it?
5) Friend behavior - First off, who are my friends, really. I hope whoever succeeds at doing MyWare can help me figure out who I actually talk to the most across the phone, IM, email, MySpace comments, etc. Then, I'd like to be able to see at least the aggregate of what they're up to. Are they all swarming around the same local news article? This is not a database that needs to be opened... its one that needs to be created and then opened, with permissions of course.
6) Local item availability - Does the local hardware store carry sun protectant stuff for vinyl convertible tops? No? Who has this item within a 5 block radius? Searching Best Buy's inventory is cool, but knowing where I can cheap dental floss would be even better.
7) Web traffic - Most of the tools for measuring other people's web traffic are pretty crappy and never work. Why don't we call just join a collective and share that data amongst ourselves? Maybe SiteMeter needs to have a site where you can search by website like Alexa to get the traffic and do comparative analytics.