"it really depends!!" on the level of security required for the data/actions that seat behind the authentication - for e.g. for Banking and Financial services -

"it really depends!!" on the level of security required for the data/actions that seat behind the authentication - for e.g. for Banking and Financial services - a 2factor auth is a must. For average usage, mobile based auth is ok - although in that case you are relying on the security infrastructure of telecom operator, which in many country is not that good - e.g. identity theft to hijack someone mobile number is quite common.