I don't see that, at least for my own experience.
I moved a Google Apps Email account for my friend's company (5 users) back to Exchange 2003. I used the free ASSP (Anti-Spam SMTP Proxy) to filter the spam, and found that the mail server got about 10 spam attacks every minute.
The IP addresses came from different counties all over the world, Russia, China, Korea, Brazil, Germany, Armania, Taiwan, Japan, and U.S. of course, etc..., you name it.
I really wonder whether an infected server in the same Verizon subnet are sending out those spams, or how these SpamBot find your server.
I do know one of the previous employees keep registering her name all over the net hoping to get some coupons/good deals , maybe that's why.
Goolge actually did a very good job filtering spams, my friend's company just want the Exchange experience back.