I agree with the web based approach too, and maybe I'll do a combo of both. I usually focus on applications that communicate with a centralized database, which would give me the ability to write a Mac app, idevice app, windows app, and web all that all talk to the same source. I do also think there will be plenty of people who would want to keep localized data rather than centralized for the purposes of privacy and safety of their data... There is a neat idevice app called ibrewmaster that brings some recipe sharing features but it's a pay app and I'm really wanted to contribute to our awesome community and fill this niche.
I've got to figure out a good way to get some dialog going so I can design this with everyone in mind rather than it be one dimensional based on what I think people want.
I'm also wanting to bring current technology into this, I have the resources, but want to make something practical, not too complex, and something that compliments the other great software out there (beer smith, beer tools, ibrewmaster, promash, etc.)