When websites say "Please log in with your Facebook ID", they're trying to make things easier by using your existing log-in. But they aren't Facebook, so can you trust them?
Of course not! However, there are systems that allow you to sign in securely across multiple sites using a common log-in. They're called "federated ID".
These trusted third-party systems can even confirm your entitlement to use a service without identifying you by name. Instead, you use a pseudonym, protecting your privacy.
David Simonsen is the manager of Where Are You From (WAYF), a Danish electronic identification system. In Patch Monday this week Simonsen tells Stilgherrian that pseudonyms are already being used in Austria's public health system and in Denmark's education system.
And we have our first audio comment. A Scientologist tells us precisely what he thinks of the protesters from Anonymous, the kind of people who ran the denial-of-service attack on Parliament House we covered last week.
Plus we have Stilgherrian's idiosyncratic wrap-up of the week's IT news.
To leave an audio comment for Patch Monday, Skype to stilgherrian, or phone Sydney 02 8011 3733.