Jonathan Rochelle, Product Manager of Google Spreadsheets recently posted the google side of the story. Here is what he had to say-
They can have real power, but there are equally real drawbacks to collaborating and sharing them. This fact led our little team to explore making spreadsheet software, and the spreadsheets themselves, available on the web. And now, Google Spreadsheets is available as a limited test on Google Labs. Even when it was only partly developed, we used Google Spreadsheets (alpha!) to manage our task lists, our feature lists, our bandwidth estimates, our storage estimates, even our complex team event voting . We now know the true meaning of "share."
Now when I say “share,” I don’t mean “send group email,” and I certainly don't mean "time-share". (That’s actually the root of the problem we are trying to solve: multiple out-of-sync versions that are email attachments.) I do mean “use and update the same spreadsheet.” When I use Google Spreadsheets to organize events with the other parents at my kids' school, we’ll be looking at the same details at the same time. If I change the agenda of next Friday’s teacher’s meeting, the other parents will see that change immediately. When my brother-in-law’s bike club uses Google Spreadsheets to track rides, they’ll be in sync — and if I change the time of next week's ride, the other riders may actually show up.