Ilya's post on rabbis' (and other clergypeople's) economic ignorance reminds me of one of my pet peeves, D.C. area rabbis who give overtly ideological sermons on general political topics like gun control, environmental issues (see Sam Kazman's post My Green Rosh Hashannah), and the like.
Put aside the issue of whether such sermons are appropriate as a general rule, and whether rabbis are completely miscontruing the concept of "tikkun olam" when they claim a special Jewish interest in such issues under that heading; I have a narrower complaint. In the D.C. area, no matter how much any given rabbi studies up for a sermon on, say, the living wage movement, immigration reform, or national health insurance, there are always going to be hundreds of individuals far more knowledgeable on the topic available as guest speakers. Indeed, in many cases one or more real experts will be in the chapel as the rabbi gives a rather ignorant talk on the subject (I've found myself in that position, once).
In short, why would I go to a synagogue to hear a rabbi speak about, say, the prospects for U.S. intervention in Darfur, when I could attend a speech by a real expert at Brookings, SAIS, or some other DC venue? If the rabbi has some wisdom to impart regarding how Jewish law and/or tradition specifically speaks to the topic of his sermon, that's another story. But in my experience, most of these sermons are more akin to a bad op-ed written for a general interest newspaper, and can only be attributed to some combination of laziness (much easier to write up a quick talk on gun control than the philosophy of the RAMBAM); pandering to the overwhelmingly liberal congregation; misusing the pulpit, in a rather inefficient way, to further one's own political ideas; and rabbinical frustration at not being a real "player" in DC.