We live in a world where our online IDs are in the hands of the government and banks, and we rely on them to keep it secure. Blockchain IDs on the other hand, put you and you only in control. Therefore, you can store all your passwords and any other personal information on the blockchain, eliminating the need of passwords in everything. In the future, these ID services could be applied to government services, medicines and any other record keeping agency.
Blockchain system exist to combat greed and middlemen and to give individuals ultimate control of their identity and activity. In a blockchain future, we will see a world where our medical records are immediately available if we are in an accident; where online voting was possible; and where transparency was paramount and greed is disincentivized.
I do not know the relevance of blockchain in ID. But I think it may help a lot in different things today since we need right now is transparency. Blockchain technology will give us an adequate information on which, what and how a certain thing happen. If there is a blockchain technology, we can easily grab the data we need and it assure us that voting or election will not be corrupted by candidates.