I've noticed that Broken Link Checker spoofs an IE7 user-agent string when checking links. Is there a reason for this?
I would suggest that this is not good practice, and that it would be better to use a user agent string that transparently identifies Broken Link Checker/WordPress. That way sites can account for it when performing analytics etc.
You might argue that some people will specifically block the link checker - well, they might, and they have every right to do so. Besides, there are many people who do the opposite and block bots/IPs that appear to be masquerading as real visitors.