"I must get an Android phone so I can run this" apps, such as Swype (since the discussion only includes iOS and Android), are excluded from the argument by Gruber.
Of course, that's an edge case. That's not a critical mass app. You aren't going to go to the mall and hear a someone talking about swype for android.
I actually have heard random people I do not know discussing Swype in public. It is actually a fairly big deal for hardcore texters (read: people ages 12-22 who use cellphones).