Heres a good little test on "trust seals" and order rates:
http://whichtestwon.com/archives/13504
cool to see a dif in trust seals like that....I chose the wrong one though....
Well, it is all relative. You should always test with your traffic because your audience can be different. http://blog.trust-guard.com/groundbreaking-split-test/
I picked the right one because I used to pay Mcafee 179 a month for years and when I quit I didn't lose any sales.