In the new decade is complete transparency an expected offering to prove fidelity?

Inspired by this question.

When dating is it now expected that passwords to email and social sites are to be ceremoniously exchanged as a sign of fidelity? Is this now common?

If one refuses to allow the person they are dating to ramble through every nook of their email and social site is it assumed that they have something to hide?

Alternately is it now acceptable to have to answer for anything found that can be misconstrued or taken out- of- context as suspicious even if it was posted or sent by another person and not written by the account holder?

I am curious as to why this is done and why simply trusting one another is not enough. Can anyone explain if it really is a benchmark for trust and commitment or is a sign of insecurity?

Personally, though I have nothing to hide in the least, I would not offer up my social passwords to my soul- mate nor would I expect such information to be given to me. Perhaps that is just us but we each have our own private space and this does not interfere with our intimacy or trust. That being said I am very curious as to what is becoming a norm- if indeed it is.