Allowing reviews only from active accounts could at least alleviate the problem and in case of Google it can even check the account's activity via its various s

Allowing reviews only from active accounts could at least alleviate the problem and in case of Google it can even check the account's activity via its various services. A google account cannot really be low activity if its owner browses the web, watches youtube, etc. The tiny minority who logs out of google when browsing, etc. could not leave a review, but it may be a small price for more valid reviews.