I got an email today from Gary Cornell (Apress publisher), who told me that they had decided to split their blogs out into individual blogs, based partly on my comments about group blogs.
That triggered another thought about group blogs, something I didn't realize I'm doing.
When I first start reading a blog, I put it on a sort of "mental probation", until I'm convinced that it has content that's worth my while to read. What I realized is that I base this probation on a specific number of posts - if it hasn't gotten interesting in <x> posts (where <x> varies, but is probably less than 10), I'll unsubscribe.
For a single new blogger, that will normally get over their initial rough posts, and give me a chance to see what they can do, but for a group blog, I may be seeing 3 people ramping up at the same time, so I'm more likely to stop reading.