You don't have to comment or post immediately. In fact, the better plan is to listen for a while, get the feel of the conversation before jumping in. But DO JUMP IN, because your current position of ignoring social media is about to become a "liability of ignorance."
So, take heart, you can go from what ever degree you just earned and get into communications and it will help every presentation, every email, every contract you have to write from here on out. AND if you are so inclined, Social Media is pretty much based on writing. If you can WRITE, and write well, you have a head start over everyone else, regardless of your degree or desired specialty.
And the real question is, IF YOU DON'T HAVE TIME TO BLOG, what are you doing with that time? I would argue that A BLOG IS MORE IMPORTANT THAN A RESUME in today's job market. If you don't have an opinion about what's going on around you, perhaps you don't have a perspective at all. And that's not good. People are hired for their perspectives as well as their track records.