When you're looking at why companies might be reluctant to use social media and blogs properly, and why measurement is so important, it's important to remember there's a very real cost involved to them.
It's something I'm acutely aware of, both in my professional role, and particularly in my personal life at the moment. My blogging and use of social networks has definitely been affected by my other commitments, whether it's doing work on our house, sorting the bills, fixing the cars, or taking care of our pets. And the biggest commitment is to our baby son, which has had a big effect on how I can justify spending time online.
And in my professional role, I'm very aware that although implementing social media work has no direct financial cost, it has a real cost in terms of allocating time and resource.
Just as I wouldn't expect to pay for something I didn't receive, it's unreasonable to expect a company to pay for for staff, and all the additional costs (office space, broadband, etc, etc,) to pursue social media engagement without them receiving a return which exceeds that value (increase in sales, website traffic etc). That's where planning, measurement, and being realistic all come into play...
(And even this post has taken twice as long as it used to, due to my son needing attention!)