Here's the one and only Justin Bieber with his Macbook Pro:
omgomgOMGitsjustinbieberJustinBieber
JustinBieberJuuuustiiinBIIIIIEEEEBERRRRRRRR!!!!1!eleventy
...Oh, sorry about that. I don't know where that came from; I'm not a nine-year-old girl or anything.
Oh well, more power to him anyway; he's not screechingly bad, and did win some awards recently. If he can avoid "going Lohan", he might turn out to be a respectable artist in the coming years.
EDIT: And now for my own celebrity contribution.
Here's musician Howard Jones with his keyboard/studio technician Robbie Bronnimann (who is also part of the electronic duo known as dba), as seen in an interview for Sound On Sound magazine. Note the Mac Pro under the production desk.
Behind Robbie's head is an iMac.
Here's a shot from a live HoJo performance. Robbie is using a MBP to drive sequences, softsynths and effects. Sometimes when Howard is touring outside the UK, he'll use just a Roland Fantom and the MBP. (Howard is a big Roland fan as well; he loves his Jupiter-8.)