I can safely establish that I hate being sung to.  It has happened to me twice in my life and it was tremendously uncomfortable and awkward.

That being said, there are very very very few people I would allow to grab a guitar and serenade me.  Deep-voiced country singer Josh Turner is on that list.  And now, so is my man Jeff Bridges.  He would just be having so much fun, no awkwardness would even register.