We usually try to exchange email a few times, and if possible chat online to get a feel for if someone is genuine. But in general, once we decide we'd like to get to know them better, we don't have an issue with providing them our phone.
...after all, lots of people we already wish didn't have our phone call us every evening around dinner time trying to sell something
But seriously, we try to get to a point with the folks where we've introduced eachother via online methods, such that when it comes to the point where we are arranging a meeting, we don't feel uncomfortable.
I guess it all depends on each encounter... and your comfort level.
al&denise