tedster - 7:39 pm on May 18, 2011 (gmt 0)
to serve as the signal to google that I want to separate myself from these sites.
If serving a 403 depends on the referer (as in the .htaccess code above) then Google will never see it because googlebot does not send a referer string. In fact, googlebot does not actually click on links. Instead Google uses the bot to compile a list of discovered URLs, and then their complex crawling logic schedules crawl lists taken from those URLs.
Googlebot is not a browser. The htaccess code above will only affect requests made by a browser whose user clicked on a link.