Is Hotmail blocking Gmail invitations?

A friend sent me an invitation to Gmail last week to my Hotmail email account but I never received it. He later sent the link to me via MSN Messenger. He jokingly said that Hotmail may be blocking Gmail invitations.

It seems that this is something even others have experienced. ZDNet has an article about similar experiences.

The article quotes MSN product manager Brooke Richardson writing in an email that
"MSN Hotmail treats mail from Gmail accounts in the same manner as all other incoming mail."