I can't find the post about this from maybe a week or so ago -- but I'm pretty sure I saw one that specifically said that the Big Apple Greeter service should not be considered "a free walking tour." The Big Apple Greeter website mentions that, among other things, the greeter will help people learn how to use the subways and find their way around the city.
Then today I noticed this portion of a post by Bigapplegreter1 (in the "FDNY tour" thread):
So, here's the question -- if we have been to NYC before (my husband went to Columbia) and are comfortable with the subways and getting around, are we not the people that Big Apple Greeter is designed for? If we are really interested in some guidance in walking around, say, Harlem or parts of Brooklyn, would it be more appropriate to pay for a commercial tour (or do a self-guided walking tour) than request a Big Apple Greeter? I certainly don't want to usurp a free service that is really targeted at first-time visitors.