Anyone else having this problem? It's described here in the Motorola CLIQ forum, but seems to plague my Backflip as well:

Basically, you can mark a contact as a Favorite on your phone, but when the phone syncs with your Gmail contacts, the "Favorite" designation gets removed.

I've found that you can manually add a "Starred in Android" group to your Gmail contacts and anyone you put in that group via your Gmail contacts on the web will show as a favorite on your phone.... but it only works one way. You can't make someone a favorite on your phone and have that contact appear in the "Starred in Android" group.