A collection of dubious top rope climbing anchors.
Clove hitches are not a proble. In fact, they're more stable and probably stronger too. (See http://www.guidetricksforclimbers.com/index.php/appendix/78-gtc-articles/78-use-and-abuse-of-the-clove-hitch and http://www.geir.com/mythbuster.html). And remain stable while adjusting unlike bowlines, but that's more use in soloing systems and suchlike than topropes.
The DoD study didn't come out of thin air. In a top rope situation, the anchor is weighted and unweighted constantly, making slippage likely.