There has been some debate here, and on other rugby forums regarding the Lee Byrne yellow card, and whether or not it should have been given. Opinions range from "just a penalty" to a red card.
From a referee's perspective, Byrne could and should have got a a red card, not necessarily for the inherent danger in the tackle, but because of an iRB memorandum to referees (dated June 2009) regarding Dangerous Lifting Tackles. I have attached the memorandum for anyone who wants to read it, but the essential part is the summary,
There is no doubt that Byrne lifts Donnelly off the ground; that is clear for everyone to see in the video...
He then loses control of Donnelly, who crashes to the ground.
Byrne and the Welsh captain argued that it was accidental, and to be fair, perhaps his loss of control was not intended. However, from the moment Byrne lifted his opponent off the ground,
he became responsible for what happened to that opponent. It was only sheer luck, or perhaps Adam Jones' presence of mind, that prevented Donnelly hitting the ground head first.
IMO, Kaplan erred on the side of leniency. He should have red carded Byrne, and will probably get a bollocking from his Match Assessor for not doing so.