Competition can be limited not only in "hard" way (like not allowing any third-party apps), but also in many "soft" ways.

Google uses his position to set default options for apps and this mean he gets all "unconscious" (and too lazy) users. This is unfair (not backed by any real superiority of his apps) advantage. Yandex tries to change default options for some vendors and Google again uses his position to limit it (limit competition). I'm totally for users making conscious choice, but with status quo it is unconscious choice and skewed in the way that gives Google unfair advantage.

In generally this Yandex vs Google reminds me AMD vs Intel case [1] when Intel used his better position to limit competitor without having real superiority.

[1] http://en.wikipedia.org/wiki/Advanced_Micro_Devices,_Inc._v.....