Miley Cyrus and Liam Hemsworth have been in love and the fire has obviously not died down. They seem to be picking up right where they left off. They are young but they have seen and experienced more than all of us, so I have no problems with them moving quickly. Enjoy kids.
I think it is understandable that a married couple should live together or it means their marriage may be having little problems. Of course each can have their individual lives with families, friends or work partners, but they should go back to the marriage home to cultivate the marriage with their partner.
Let's face it, they are both adults. They can both make their own decisions, and frankly, all of their information that they want people to know is public....well mostly. We have no idea what kind of private conversations are happening with them, and they have made the decision to move in after they have had some in depth conversations. It is the pattern of today to move in and "get to know" each other before any kind of solid commitment. Let them be!
I don't think it is anyone's business but theirs. People need to stop interfering with others happiness. It is their lives to either be happy or make a mistake with. If people would mind their own business they would be much happier with their own life. I wish them both luck whether they are together or not.