Saturday my car started making a "bap-bap-bap" tapping noise. People who heard it said "hey, is that a diesel? It sure sounds like one! Heh, heh."

It sounded like it was coming from the top of the right-hand cylinder bank. I had it towed to the dealership, where a mechanic got into it today and said one of my lifters had collapsed. All the lifters were replaced, all under warranty, and no other harm seems to have been done.

Question: is this a common malfunction for an '02 E55 with 11,000 miles? How worried should I be about a repeat, or about something else causing it, or about running it for a while like this damaging something else?

Thanks,
Mark.