This isn't the first time I've heard about such things, but this is definitely closer to home than before. If a random company in Auckland is working on a big XUL intranet app, then how many other such projects might there be? One might guess hundreds or even thousands. This is rather disconcerting for several reasons. These projects have no visibility in Bugzilla --- why aren't they filing bugs? We don't really know anything about these projects: how many there are, what features they use, how we're hurting or helping them. Gecko development is totally ignorant of their needs. But how can we find out since these intranet apps by design never become visible to the public?
Maybe it's a good thing in some ways to not be giving much attention to these apps. It means we can focus more on Firefox which is more in line with Mozilla's mission of driving the Web forward. And we certainly haven't promised much to XUL app developers. Still, it sucks to cause pain for people, and if there are thousands of XUL apps below the waterline and we could support them better in simple ways, I want to.
For one thing, our Q&A for XUL is basically "do Firefox and Thunderbird still work?" This sounds inadequate now that it seems likely that Firefox and Thunderbird are less than 1% of the XUL apps out there. If we had a lot of unit tests for XUL that would give us some more confidence that we're not breaking things ... or at least that if we are breaking things, we do so deliberately.
The other thing we should do is think about how to harness the power of this community that probably is quite large and influential ... even if we can barely detect it.