I've been told by some friends that they were unable to make a comment because they have to join google or one of other groups in order to make a comment. It's obvious that google wants you on their books but seriously, you do need a login from one of 3 companies so that your comments can be traced. This is probably to minimise libel for which the hosts may be responsible for.
As a responsible person you should have nothing to fear from this but it's your choice. The President of the WPM makes useful advice and accurate predictions from comments he gets from other sources. But the more the merrier.
