Sorry for my language.I'am italian.
Many people with high ranking play like guest.
I think that this should be not possible because the difference is great and often play the games in not funny.
Why administrators don't stop this possibility ?

Personally I dont have a problem with it. I use the guest feature alot for a quick practice say and especially when I have problems Logging in to my account at least I get a game!

This is a feature for premium members, so no premium member is doing anything wrong, we're using something that comes in the package.
None premium members can also do this by having a few games as a guest, then maybe logging in properly, there is no rule that says players who are signed up can't play as a guest before hand.
Also, people may play from the same IP address, so where one may play as a member, another may just play as a guest. Therefore, there is no way of determining which member of a household is playing as a guest as it would be a pure guess, especially if there are several people using the same IP address.