I think it's good idea also, really tells you about the person coming to the country, only problem is they may delete prior posts of theirs. I support the idea lol, do anything to get an edge on the visa applicants. They should figure out ways how to get the social media account without actually letting the applicant know why it's wanted so it doesn't raise alarm bells on their side and won't lead to deletion of their post and at the same time fitting in within legal requirements of privacy and disclosure.
But a person can really be judged by what they post on social media, their in their comfort zone and their real views and opinions come out. They will just need to siphon out the trolling bits and add up their real posts and compare against their words on the application and interviews and see if the person adds up or not. You can't trust someone anymore just by their words, they need much more mechanisms to balance against.