weak or unowned?

[LucasVanDongen]

I'm trying to understand better how to work the best way possible with ReactiveKit. One of the things that I know I should do is make the reference to self weak in blocks live observeNext. However it seems to me that it's quite rare if not impossible that the ViewController my ViewModel belongs to really became nil when one of these blocks gets called. Is it 100% safe to use unowned instead or am I missing some edge cases where my app might crash?