1. I don't have time.
Do you make time to go to network meetings? Or to design a leaflet? Then you can make time to "do" social media. Take a long thin slice through your week. Now you have time.
2. I don't know what to say.
Remember those network meetings & marketing leaflets you make time for? Use those as a basis for your initial few weeks. You know your business and the questions people want answers to. You have a lot to say. Your problem could, in fact, be selecting what to use!
3. My customers don't use Twitter/Facebook/LinkedIn etc
Perhaps it's true that your current customers don't use social media. How many more do use it? More to the point, how many people that can refer you to new customers use it? Do you know, or are you guessing? How many of your competitors are ahead of you?
4. It's too risky & uncontrolled
So is all networking, you're just used to the ways of managing the risk in the more traditional formats. Transfer what you already know into the new arena.
5. There's no evidence social media works
Yes - there is. Quite a lot of it in fact! There are whole blog sites literally groaning under the weight of evidence. Good places to start are sites like Unmarketing and Social Media Today.