On Windows machines, there is a way to circumvent CasaleMedia and other such sites with a hosts file. It works by redirecting known spam and malware sites to your own computer.

http://www.mvps.org/winhelp2002/hosts.htm

The usual result is that where the web site using their service allows space for an ad, you get an error message that the file can't be found. Occasionally it is necessary to disable the hosts file because some websites won't work without the offending sites, but for me (at least) it's
worked very well.

It is necessary to download a new file periodically to keep current.