I am an unabashed yelp advocate.
I am on yelp and have received contact after contact after contact. Both buyers and sellers. And much to Yelp's chagrin, I do not pay them a dime. I attained visibility on yelp by having clients post testimonials there. I have a equal amount of reviews that are visible, and an equal amount that didn't pass Yelp's logarithm, and found themselves listed (as I call it) below the fold.
That being said, yesterday I received a call from a potential seller who found me on Yelp. I tried to call him back, and send him an email through Yelp, but he didn't respond. Fortunately, he had included his telephone number, so today I phoned (and left a voicemail), as well as texting him.
He did return my call, and I'm going to meet with him tomorrow, but he told me an odd story.
After sending the direct Yelp email to me, within moments, he says, he received telephone calls from eight other agents (including a colleague of mine in my own office). He was so discouraged... because he thought he'd reached out directly to me... that my response kinda got buried. He thought my response was just one of a myriad of hungry agents.. so he ignored them all.
I guess that Yelp has its own version of "Premier Agents", and apparently a direct contact in Yelp may be direct, but is more of a "party-line". Be aware.