Overall there will be nine major conferences in 2010 with a Call for Papers. So I did a analysis of the topics mentioned there, I did not include general conference slogans.
On average every Call for Papers includes 17,7 topics, ranging from 11 (CSCMP Europe 2010) up to 32 (8th International Heinz Nixdorf Symposium).After aggregation of those 159 topics into 26 themes, it results in the following ranking.