Google Adwords is profitable for me but not by a large margin. By checking the box "search sites in Google's network" (under Distribution Preferences in Edit Campaign Settings) it turned into a money-losing proposition.
Here is a table of click counts from Friday for all the domains that Google calls "search sites":
(all others) 177
comcast 10
google.ie 10
earthlink 11
aol 17
updated 19
msxml.excite 21
metacrawler 24
ms101.mysearch 26
google.com.au 38
groups.google 46
dogpile 56
google.ca 99
google.co.uk 111
netscape 130
web.ask 255
aolsearch.aol 297
google 1349
-------------------- -------
total 2686
So checking "search sites" adds clicks from AOL, ask.com and Netscape primarily but many others as well.
The "content sites on Google's network" is a very different animal. From this I received very little traffic, only about 6 clicks out of 6000!
Of course, your mileage may vary.
-- Bob Stein, VisiBone