Unfortunately they're no incentive for interoperability. In fact there's a strong disincentive for it. The value in these companies is the captive audience and

Unfortunately they're no incentive for interoperability. In fact there's a strong disincentive for it. The value in these companies is the captive audience and the network effect that makes users sticky. There's very little money in producing a commodity chat client (a la Pidgin or Adium). It is in all of these companies' interests to not work with each other, as their only value is the size and exclusivity of their userbase. Personally I just SMS now. I'm sick and tired of installing apps just to talk to that one friend who uses it, especially when SMS works just fine.