Hey this is a pretty sweet idea, I like where your head is at. Not only would you get to upvote and write some comments but you'd be introduced to their social profile / blog. I don't know about you, but I've met some pretty interesting taxi drivers in the past and would enjoy learning more about them and maybe learning more about their city. Then what would have been a few dollars tip becomes a longer term way to support that person via steemit. Essentially it's a social tip :)