I don't think it's just about e-mails and phone numbers. E-mails are a dime a dozen, you can make a new one anytime you want specifically for /out/ planning if you don't want to post your main. You don't even need phone numbers because you can simply use e-mail over your phone.
No, the problem lies else where: taking the responsibility to actually organize the event. There needs to be someone who takes charge and makes sure the information is distributed for all people. They need to set the times, the location and take care of all the fine details.
I see two ways to actually make these happen. The aforementioned, someone grabbing the responsibility by the balls and taking the information and distributing it. The other, a website where the information is centralized and can be discussed amongst the people attending the event. The latter is harder to do on a website like 4chan because threads are decentralized.. they come fast, they go fast. Again, unless someone takes charge and makes constant threads following up to the event, it's going to fall off the board and forgotten about.