Today there is an article on this subject on GeekWire. There's also been a discussion going on on Geekestate.com on this subject. It appears that this is a rapidly evolving real estate marketing issue that real estate photographers need to be aware of mostly because it's likely going to be a hot issue for your clients.
With this syndication backlash going on clearly you are not going to want to be automatically syndicating tours to all sites. There may be a benefit to be able to control specifically what sites. Realtor.com, Zillow.com and Trulia.com seem to be the sites at issue.