There have been some comments recently (here and here) that it is possible to attack a third party by a number of methods including redirecting a banned domain to a good domain and dumping poor quality links on a site.
My suggestion to solve the redirect problem is to authenticate any domain to domain redirects in the webmaster console.
So if Black hat A redirects badsite.com to good site.com the good site webmaster B using webmaster tools can repudiate the redirect.
Another possible attack vector is adding links from banned for poor quality domains maybe webmaster tools could display the rate of link acquisition and flag and big changes from the long run or a beta from the normal rate
This would allow a webmaster to investigate if anything dodgy was going on and again you would need a way for webmasters to repudiate links from sites they don’t want – maybe at a domain level in webmaster tools.