Did Justin Diss Britney?

Last night, while introducing Madonna at her induction to the Rock 'n Roll Hall of Fame, Justin Timberlake made some not-to-subtle references to his ex, Britney Spears.

According to Us, Justin mused that "the world has always been full of Madonna wannabes and I might have even dated a couple."

Calling his troubled ex a "wannabe"? Nice.

He then went on to say about the Material Mom that "she has still found time to kiss someone I may or may not have publicly kissed myself while I was in the audience. Of course you know I was talking about Sean Penn."

Is it really kosher for Justin to be taking these kinds of jabs at Britney when she's so obviously down?