I've got an invitation to HackerX. I didn't think it was particularly worthwhile after I've got a repeat notification seeing as I didn't register on the first one, but decided to check it out. By the way, I don't know where did they get my address from - during the registration I was asked for LinkedIn and GitHub so perhaps not from there.
The event itself was crowded. Perhaps 50 people in the room, and that's considering a lot of name tags didn't get picked up. About 15 companies, the only familiar name was Telstra.
But that's not the main thing. During the registration they let me choose my programming languages, asked about GitHub and LinkedIn, but after the introduction they just let everyone take a spot at one of the employers' desks at will (5 minutes to a company). So, as I understand it, there was no matching of companies to developers based on interest - just a career fair.