This relies on the voter to have enough autonomy to be able to independently access their online ID. It would be easy to circumvent by separating the voter from their ability to identify themselves online. Either by keeping their means of identication from them during the voting period or by being the gatekeeper to the computer where their online ID is stored, for example with a password.

It also relies on the voter caring enough about their vote in the first place to be willing to attempt to do it, with whatever possible personal risk that entails.