Im sure lots of users have the same problem or they didnt noticed that yet.
Go into the admin panel - > Change Settings - > Member Settings - > Check this field " Require new reviews to be approved before being listed "
Go to your skins folder, find rate_form.html, before you edit rate form, make sure you add into " child " folder.
You can now completly remove all the code there, or you can add some tricky words for the spammers
For the users who didnt know about this review spam, you can check: