Now, I don't see how pure MFA sites could report any conversion stats. SmartPricing is tracked using a script that you run on so-called "Thank you" pages (e.g. pages shown after purchase or other actions considered as conversion). Pure MFA sites display only Google ads. Hence, they have no "Thank you" pages and they can't use the SmartPricing tracking code.
If MFA sites cannot report their AdWords conversions to Google, then your AdSense earnings can't be affected by SmartPricing caused by MFA sites.
The bottom line, blocking ads that link to pure MFA sites can't affect SmartPricing on your site in any way (maybe only if the MFA sites edged out advertisers who do track conversions -- then you could actually earn more thanks to MFA sites).
(Disclaimer: I do not approve MFA sites. Sites without real content are spam.)
[edited by: John_Carpenter at 2:51 pm (utc) on Mar. 23, 2006]