[atourino]

Not only that, but more importantly, on Twitter you can follow pretty much whoever you like without a required acknowledgment from the followed person/organization. To be friends with someone in FB, both parties have to agree, which pretty much sets them apart niche-wise.

[ivey]

Twitter's asymmetric follow is one of the killer features. GitHub has it, as well...maybe if GitHub had a status API they could be a Twitter killer.