In version 1.6 all Product Tags are included in the Tag Cloud even if Nop_ProductTag.ProductCount = 0. If a user clicks on one of these tags, they're brought to an empty page (since no products are tagged with the tag). The user then becomes confused because what's so popular about a tag that has no products associated with it.
The SP Nop_ProductTagLoadAll should also include a check for ProductCount>0 which will eliminate this problem.