Why are official announcements of presidential campaigns moving slower this cycle? Does it tell us anything about the 2012 election?
I'll take the second question first...I think it's very unlikely that it matters, in that sense. It's incorrect to say no one is running yet; what's happening is that formal announcements, and perhaps some other formal steps, haven't happened. Yet of course Tim Pawlenty, Mitt Romney, and others -- including Sarah Palin -- are running for president, at least for now. They're basically doing the same things they would be doing had they announced their candidacies.
So, why the lack of announcements? It may be really be the case that there's a larger-than-usual group of ambivalent candidates, politicians who want to run, but aren't convinced that this is the right cycle for them, and don't want to be labeled quitters or losers if they back out later in 2011. It may be that changes in fundraising or changes in the media environment have changed the value, or perhaps the optimal time, for making things official. One or both of those things could be concentrated in longshot candidates, who typically announce first. That's because longshots are most in need of being "taken seriously," which they need in order to win endorsements, raise money, and otherwise gain support. Typically, longshots also need name recognition, and an early announcement has traditionally been seen as a good route to national press coverage that otherwise is hard to come by.
So, Tim Pawlenty may feel that an announcement is superfluous. Getting in officially isn't going to make GOP opinion leaders take his campaign more seriously than they do now. A similar story may be the case with John Thune. Rick Perry may just be taking some time to retreat from his election-cycle-based claims that he isn't running. For all three, the efficiency of the partisan press may suggest to them that when they time comes, it won't be hard to get their names to less-attentive primary voters. For the fringe candidates (Dave Weigel mentions Herman Cain and John Bolton), there may be plenty of access to free media that doesn't depend on whether they are actual candidates or not.
All of that changes once the debates begin, which won't be long now. At that point, the fringe candidates and longshots certainly should be in, because they won't want to pass up the chance to appear on even terms with the leaders of the field. In turn, the leaders won't want to lose that status by allowing someone else to "win" a debate and move up in national horserace polls, so they'll have a stronger incentive to formally announce.