My view is a little different than Brad's. I would say that economics is really, really, really, really, really, really, really hard. And that's leaving out a few of the "reallys."
It's so hard that experts don't always do it well. The experts are constantly prone to correction by non-experts, by practitioners, by people who are self-educated economic experts but not professional economists, and by people who know some economics and a lot about some other field(s). It is very often that we -- at least some of us -- are wrong and at least some of those other people are right. Furthermore those other people are often more meta-rational than a lot of professional economists.
Even very simple problems can be quite hard, such as why nominal wages are sometimes sticky or why particular markets don't always clear, in the absence of legal impediment. Why doesn't the restaurant charge more on a Saturday night? You can imagine how hard the hard problems are, such as what level of public expenditure is consistent with an ongoing and workable democratic equilibrium.
Putting aside agreement and ideology, and just focusing on how one understands an issue, I'll take my favorite non-Ph.d. bloggers over most professional economists, six out of seven days a week. Not to estimate a coefficient, but to judge public policy, thereby integrating and evaluating broad bodies of knowledge? It's not even close.