There are a variety of reasons people seem to like to get their hate on at us, especially Markos, and I'll try to spell them out as I understand them without bothering to argue with them.Of those, I'd say 2, 3 and 4 are simply the nature of the beast; you support candidate or cause A, and supporters of candidate or cause B will get upset. Kos, especially, is feeling the heat for that right now. 1 is definitely not true, since many of the uber-blogs on the left are relatively new (like FDL and C&L, both of which came after 2004), and Kevin Drum has been around awhile without resting on the laurels earned back in 2001-2.
1) A-list bloggers have shitty blogs that no one should read but people just read them because they've been around for so long.
2) A-list bloggers are supporting the wrong candidates/causes. They are doing X, but they should be doing Y.
3) A-list bloggers suck up all the attention from better bloggers who everyone should be reading.
4) A-list bloggers end up representing the "netroots" but they shouldn't.
5) A-list bloggers aren't generous enough with their links and should be providing more publicity for other bloggers.
6) A-list bloggers are stupid and they're ugly and nobody likes them.
5 and 6, though, are definitely true, and is one area where the Right has us beat. The most frustrating thing for any blogger starting out is to get attention, but conservative bloggers have the good fortune that people like Glenn Reynolds, Mickey Kaus and Hugh Hewitt are very generous with their links (perhaps too generous; it would have nice if someone had bothered to perform due diligence before linking to Thomas Lipscomb several weeks ago), sending traffic to many different sites every week, and nurturing allies for the future. These guys get lots of e-mails, requesting or demanding that they link to one thing or another, and lord knows that must be terribly annoying, but they still manage to spread some of that wealth around.
And if you've sent such an e-mail in the past, of course, there's nothing like receiving a rude response, or having an "A-list Blogger" (cute terminology, btw, straight from the Social Register) cite something of yours without giving you credit, to ensure an enemy for life. It shouldn't be any surprise that the lack of civility, of common decency, towards one's adversaries that has become so endemic in the blogosphere, should also reflect an unpleasant personality by the blogger. As Richard Nixon might attest, and as George Bush has discovered the past eighteen months, if you've kicked a lot of people on the way up, your inevitable fall is going to be pretty ugly. Your enemies will do what it takes to get even, and you'll find out that you made fewer friends than you thought.