Hey Mark -- one of the WhereBerry co-founders here -- we think you are right on the money. We also find that having a persistent list of activities you want to do helps make that activity actually happen. Cheers!
Mark, that's too funny. The idea for WhereBerry came from my own Google Spreadsheet, creatively titled "Concerts I want to go to". Turns out a lot of people have these...
Great job with the site! This space is definitely in need of some innovation. I actually immediately thought of Plancast, but WhereBerry seems to be focused even earlier in the decision process (I want to do this, but don't know when). My current solution is a trusty Google Spreadsheet called "Things to do in SF", but that is not social at all.
I've been waiting for something like this for a while. Now, although there is too much noise in something like Facebook or Twitter, I run into the case where small apps like this don't have enough saturation into the market and so it doesn't work out for spontaneous events but rather acts like something I post into Facebook Groups. Speaking of which, it would be nice since there's already Facebook connect to grab my friends so I don't have to manually look up their emails and invite them.