hybrid cars - celebrity list of hybrid car owners

I was reading the blog hybridcars.com and they had an unconfirmed list of hybrid cars owners. Is there any way to really tell which celebrities own hybrid cars, besides seeing them drive the hybrid cars?

Here's an unofficial, unverified, and incomplete list of actors, singers, and pundits who were early adopters of hybrids.

Alexandra Paul
Alicia Silverstone
Dr. Andrew Weil
Arianna Huffington
Bill Maher
Billy Crystal
Billy Joel
Brad Pitt
Cameron Diaz
David Duchovny
David Hyde Pierce
Donna Mills
Donny Osmond
Ed Begley
Ellen DeGeneres
Ewan McGregor
Hart Bochner
Harrison Ford
Jack Black
Jack Nicholson
Larry David
Kevin Bacon
Kirk Douglas
Kurt Russell
Leonardo DiCaprio
Dr. Oliver Sacks
Patricia Arquette
Prince Charles
Rob Reiner
Robin Williams
Salma Hayek
Susan Sarandon
Tim Robbins
Ted Danson
Tom Hanks
Woody Harrelson
Will Ferrell