I'm surprised at my reaction to Backpack. I'm finding that it feels too clean, too packaged for something to which I could want to commit so thoroughly. I love 37signals' work, but I feel like Backpack's weakness is its failure to deliver something as open as the technologies from which it descends, namely blogs and wikis. The Backpack/Basecamp idiom is polished-looking, which is great for many purposes, but for me it doesn't work for brainstorming and other "raw bits" purposes that comprise what I need to do with what's in my head. Backpack suggests a larger integration of technologies and use cases than has been accounted for, and its ideas reach well beyond the scope of a single product.
I want an Ajax scratch pad that can share, email, receive mail, name URLs, remind, integrate fluidly. 37signals showed us how this can be packaged slickly. I'd like to open this idea up for a lot more collaboration and a lot more freedom.
I felt this way already, but Adam Bosworth of Google recently spoke about four criteria for evaluating whether a web technology will catch on: "Simple, sloppy, standards-based, scalable."
Backpack is standards-based. I've discussed a desire to make a sloppy version. I bet the remaining criteria of "simple" and "scalable" can be used to create something really interesting.
And towards "standards-based": what if in addition to creating and consuming email, whatever-it-is also created and consumed RSS? IM?
But also, as I complained to the 37signals team, Backpack doesn't have a clear focus. It's really slick, and its current huge success may make me look like a fool for saying so, but I don't think it's a winning idea without a better story. Whatever angle I come up with, Backpack is too big or too small, too personal or too prefab. I like the way Google is building focused services independently, then gradually tying them in to the larger Google experience. Backpack seems like several such services awkwardly rolled into one.
I'll collect ideas and action items toward the vision described above
in the comments. Please speak up if this piques your interest.