Yes, they do, because they're used to handling bad and invalid HTML from the old days. We're supposed to be trying to move away from that, not make it worse by inventing new and on-purpose-wrong tags!
Everyone would prefer an XML-based system, but we don't HAVE that yet. Inserting random XML tags into an XHTML document is not only invalid, but it messes up EVERY browser out there.
Microformats achieve the same thing, do not break the way (X)HTML is supposed to work, use what is defined in (X)HTML for semantics, and are backward-compatible to quirksmode
Perhaps microformats are only a stepping-stone, but they are a good one
As manager of the XOXO blog, I would like to make a few things clear:
1) I am not officially connected to microformats.org 2) I suck at design, but, at user request, have redesigned my blog three times. If you have any design ideas that make sense I'd be more than happy to try again. 3) Most of the XOXO information available is geeky because it is a geeky subject. When I first looked up OPML I couldn't even figure out what it was, because of geekiness. Same went with XOXO. Once I saw both of them at work in a feedreader, however, I was hooked.