From my experiences trying similar things over IRC, I have found that the lack of anything holding you to your promises definitely is a detriment to most people. I have found a few for whom that's not the case, but that's very much the exception. That's definitely a failure mode to look out for, doing this online (especially in text) won't work for many people. In addition, this discrepancy can create friction between people.
The general structure of the failure tends to be one person feeling vaguely bad about not talking as much, or missing a session. And then when they don't have many vectors to viscerally receive signals of disapproval, of the kind that would cause them to be uncomfortable and go through with it even when they don't want to, it becomes easiest to do it the next time. Schelling Fences are easier to break without face to face interaction.
There should be ways to bypass that problem. One of the memes around LW is actively reinforcing positive things, instead of relying on implied approval. If you can create a culture of actively rewarding success, and treating apathy as something to be stamped out at every point, then you can do it. You can also make a point to create norms where one goes out of their way to help someone who falls behind to figure out what the true problem is. If you can manage that, instead of silence or simple berating, then you can make it work. Ideas around Tell Culture can help you with this. Unfortunately, this also requires diverting a lot of focus into preserving those conditions. Creating community norms is hard, but that seems like the way you avoid that problem.
I don't mean to imply that you want to start a community around this along the lines of the LW study hall, but this is what I have found from my attempts. Maybe someone will find it helpful.
Briefly: I'm looking for a person (or group) with whom I can mutually discuss self improvement and personal goals (and nothing else) on a regular basis.
Also, note, this post is an example of asking a personally important question on LW. The following idea is not meant as a general mindhack, but just as something I want to try out myself.
We are unconsciously motivated by those around us. The Milgram experiment and the Asch conformity experiment are the two best examples of social influence that come to my mind, though I'm sure there are plenty more (if you haven't heard of them, I really suggest spending a minute).
I've tended to see this drive to conform to the expectations of others as a weakness of the human mind, and yes, it can be destructive. However, as long as its there, I should exploit it. Specifically, I want to exploit it to fight akrasia.
Utilizing positive social influence is a pretty common tactic for fighting drug addictions (like in AA), but I haven't really heard of it being used to fight unproductivity. Sharing your personal work/improvement goals with someone in the same position as yourself, along with reflecting on previous attempts, could potentially be powerful. Humans simply feel more responsible for the things they tell other people about, and less responsible for the things they bottle up and don't tell anyone (like all of my productivity strategies).
The setup that I envision would be something like this:
I've tried doing something similar to this with my friends, but it just didn't work. We already knew each other too well, and there wasn't that air of dispassionate professionality. We were friends, but not partners (in this sense of the word).
If something close to what I describe already exists, or at least serves the same purpose, I would love to hear about it (I already tried the LW study hall, but it wasn't really the structure or atmosphere I was going for). Otherwise, I'd be thrilled to find someone here to try doing this with. You can PM me if you don't want to post here.
1. After explaining this whole idea to someone IRL, they remarked that there would be little social influence because we would only be meeting online in a pseudo-anonymous way. However, I don't find this to be the case personally when I talk with people online, so a virtual environment would be no detriment (hopefully this isn't just unique to me).
Edit (29/3/2015): Just for the record, I wanted to say that I was able to make the connection I wanted, via a PM. Thanks LW!