Via Matt Yglesias, I see the blog Fistful of Euros has a long and interesting (but somewhat technical) post arguing that Europe is rapidly heading into deflationary territory--deflationary spirals being bad because they bring about depressions. Worse, the man who runs the European Central Bank, Jean Claude Trichet, seems blithely indifferent to the situation--indifference being bad because the central bank is really the only institution capable of preventing such a spiral. (Say what you will about Ben Bernanke's role in the various corporate bailouts so far, he's been unbelievably aggressive in easing interest rates and leveraging the Fed's balance sheet to fight deflationary pressure.)
It's a pretty huge concern given that, as Matt points out, Trichet presides over an even larger share of the global economy than the Fed.
P.S. Matt also pipes up on something I meant to get into earlier--the lunatic idea that deficit spending can't stimulate the economy because people simply save their money in anticipation of offsetting tax increases down the road. This is a rather strained view of a concept economists call "Ricardian equivalence," and Obama's chief economic adviser, Larry Summers, has devoted a few academic papers to blowing enormous holes in it. (Paul Krugman weighs in a bit here and Brad DeLong here.)
Update: Megan McArdle is also concerned. She has some worthwhile thoughts on the political and cultural context in which Trichet operates.