Network effects will definitely be the #1 challenge. I considered integrations—I first tried Pony as an email service, actually. I wanted it to be as accessible as possible. This led to a lot of problems, specifically you get this asymmetry and confusion of some people being on Pony and others being in instant real-time. All of our existing platforms come with norms and expectations, and using a non-instant integration was often perceived as anti-social, which was really unfortunate because I was trying to build something pro-social. You also lose this effect of it being a special place.
Anyway, it is hard to get people on, but fortunately the idea seems to be unique enough and resonate enough with that there's already a seemingly dedicated (albeit small) userbase. It suggests that maybe network effects will be possible to overcome. Everything has to start somewhere!