We just went through quite a bit of discussion about this issue internally. The end result was not to do anything for the moment, except we included a "submit a support ticket" system in our plugin.

Initially, I had gathered some site meta data to include with the ticket; but I realized that I was breaking a cardinal rule with interacting with customers, so now we include a "Here is what will be included in the support ticket" box with *exactly* what we're going to poll. On support tickets especially, we're virtually always going to ask the same handful of things: What version of WP are you running, what's your current theme, and what plugins are active? Now we can just gather those facts with the request.

Of course, we've tried to further make it clear that if the customer doesn't want to include that information, they can email us directly for support. Unfortunately; those are the exact things that we need for virtually any support request!

Good post though; I think as plugins & services for WP get more sophisticated it's important that the plugin & theme development communities stay in front of this. Watching the current crop of stuff coming up around this whole iPhone "address-book-gate" I think respecting our customer / user privacy & data is more important than ever. Even things that we might interpret as trivial or aggregate and unthreatening.