I've been listening to Tom Petty since I was 8, and until you said DC = MJLD, I didn't even contemplate that connection... and, now that you've mentioned it, I just listened to both songs, and I still don't see how they're comparable.
Also: I know people like to call it 'Last Dance with Mary Jane', but I must insist the title is "Mary Jane's Last Dance". -_- that's bugged me for years.
Edit: Okay, having just listened to it once again... I suppose the verse of Dani California has a similar chord progression on the guitar, but the chorus is completely different, as is the bridge, not to mention the bassline. I don't know if the songs are even in the same key, because my ear isn't that good, but I'm pretty sure they aren't.