A couple observations:
1) I think by denying LeBron the ball the C's have been effective in making him work harder than he is used to.
2) LeBron may be the best player in the league at getting to the rim, but his shooting is suspect, he doesn't move well without the ball and he has no post game.
This seems a product of Cleveland catering to him since he entered the league. They've never taken the bull by the horns and said, "hey you are a great player and all but you could be better." Instead they've taken on the get him the ball and get out of his way mentality.
3) I'd be hard pressed with Cleveland's roster to find a defensive strategy to stop the Celtics. The C's own them at two of the most important positions, PF and PG. They have no one to slow down Rondo, that doesn't involve creating a mismatch on the wing and they can't stop KG on the block. If the C's are aggressive the Cavs do not have the personnel to stop them.
4) Credit the C's defense and TT. They overplay LeBron and draw double teams from different spots, they switch off and force different match ups and they give him bad lanes. They don't make it comfortable for him and they can do it because their floor spacing and rotations have been spot on (minus 72 minutes give or take).
This has been very Bellichekian in approach, limit what they do best and make it uncomfortable for them to do it and then have them beat you with secondary players. Conversely, this has been tough for the Cavs to do to the C's and I think the dam is an apt metaphor as to why.