I had the same problem Mac late 2010, 2.13 Intel core duo 4GB RAM 2
Lion was installed as update.
CPU on 80 °C and to keep it between 70 and 80 °C fan had to work on 6500 RPM.
I used Istat.
repaired permissions, no result, reset the SMC and so on... no results.
lately reading also other posts, I started to disable 1 by 1 the start up items.
the antivirus Sophos + the time machine auto back up -on off was quite successful
now I have a 4000 RPM = quite decent as noise level and CPU at 40-47 °C.
had nothing to do with the flash or browsing, mai land so on.
Spotlight, yess is pushing the temp up, but is not running 24/7
Check your startup items, the answer can be there
I have to agree, I wish I'd jave waited. Actually good I'm reading this though because I was kind of thinking it might be because my macbook is a few years old and can't hack it. If I'd have bought a new one and still got the fan crankin I would have been annoyed. Will wait for further releases I'd say. I gues no one who hasn't yet upgraded would be reading this, if you are ( which you aren't ) don't upgrade yet I'd suggest.
Here is some additional information after I reset my SMC. I am running on a Macbook Pro 2.1. Resetting the SMC seemed to have helped a bit since it used to be especially bad after just leaving the machine for a while and it going to sleep.
Now I notice it even when just using the machine with email. I was not running safari at the time I noticed the problem again. The AddressBookSourceSync and System Preferences apps are running at between 60 and 70 % each which is my my CPU temp is very high. I have seen it in the 170s and it has never been that high before. I am afraid of what running it this hot for a long time will do.
I quit the System Preferences app that I had running and that helped, but the AddressBookSourceSync is just out of control, exceeding more than 70% and I think it should have finished its major work when I moved to iCloud yesterday.