I just spent the better part of an hour trying to figure out how to register for an event. There was no phone number, email, or registration link associated with the listing. When I tried emailing the event coordinator at the conference center, I got a form to fill out.
I really want to attend this event, so I'm sticking with it. But otherwise, I would have given up and walked away at this point. It's not clear that these people want my business. And it's not a good way to start a relationship with a customer.
Bottom line - always provide some direct method of communication for anything you post relating to your business. One click should take you to a registration link, a Facebook page, or at least an email. And provide a phone number for good measure. Make it easy for potential customers to find you, or they may not be potential customers for long.