I most definitely pray for celebrities.
I have learned that God sometimes wants us to pray for the people WE think are the most unlikely to need or deserve our prayers... but that doesn't mean God thinks they are unlikely. God has (with MUCH prompting and a LOT of work at changing my heart) led me to pray for a lot of people (men who have molested children, for example) that we, in our flesh, would find unworthy of our prayers.
One of my most beloved mentors (she was like a spiritual birth mom to me) had a heart for Britney Spears, and whenever she saw something negative about her in the news (which of course, was all the time), my mentor prayed blessings on her instead.
I have parked my car across the street from "adult bookstores" and prayed that the owners would be saved.
I prayed for Nicole Kidman when she was going through her divorce from Tom Cruise, because, after going through the pain of my own divorce, I couldn't imagine what it would have been like to have that splashed all over the front of the newspapers.
A friend of mine prayed for Kanye West when his mother died, because he had lost his mother too (and had a lot of anger issues, just like Kanye). I admit this would be a tough one for me, as Kanye is one of the celebrities I personally do not like at all, so I admired my friend's dedication in praying for him.
My father had a well-known business, and though I was never rich nor famous, people always ASSUMED I thought I was. They loved to tell me, "It must be nice to be rich," (when my dad was supporting a family of 5 on a modest income) and, "It must be nice to have your parents buy you everything," (never mind that I was going to college full-time and working 3 jobs.) I also had a boyfriend who used to LOVE to tell everyone, "Yeah, I'm with (Kim), and her dad is so-and-so, and he owns such-and-such." I HATED THAT. All my life, people loved to tell me who I was (according to THEM), how much money I had (in their own mind), and what my pampered life must be like (thanks to their own imaginations.)
And you know what? I wanted to smack them all! I can't imagine what it must be like to have your entire life broadcasted as "news". Now granted, some celebs love, live on, and purposely pull in the attention. But others, I truly believe, are people trying to live out their lives and happen to do so in areas that automatically come with the celebrity.
In a very small way, I feel like I got to see a small glimpse of what some celebrities must feel, and when I read that someone famous has attempted suicide, I always pray for them, because it's something I can relate to.
God doesn't tell us to judge... but rather, to pray, uplift, and bless. If God calls some to pray for everyday people, great. If God calls someone to pray for celebrities, wonderful. And if God calls some to pray for both... I personally believe that as long as we're all following what God wants for each of us, we're all doing pretty well.