So many people in the world and not enough names!
You can always have something in the front of your book along the lines of "This story is completely fictional and any resemblance to any person, either living or dead, is entirely coincidental."
But... if you use the name of someone you know personally, they could probably argue in a court of law that you've deliberately used them. If you use a name and don't know anyone with that name, however, I'm pretty sure you're safe.
Hope this helps