The cost of investing in social media will decrease

There is a lot of talk in the blogosphere about measuring the ROI of social media, but what about the I? In order to find the return on your investment, you'll need to know how much you invest. Now this is far easier to meassure than the return that comes out of social media as on of numerous factors impacting your business. This is where I had a Flash Of Genius (a great movie about the guy who invented the intermittent windshield wiper just to fight Ford over it for decades). The investment in social media can be to hire two guys to do it, or it can be to hire a consultancy company. This investment is measurable in terms of dollars or euro or yen. Here what's wrong with this methodology:

Large companies are doing social media as an added business function to what they are already doing. There seems to be no down scaling as a result of other activities as a result of social media. The phenomena of social media is still too new for companies to trust it to do its job properly. It's not a one-to-one relationship between the amount of social media marketing and real life marketing a company is doing. The sum of social recruiting an real life recruiting is not constant. When these trust issues are overcome, social media will replace some activities currently done in real life, reducing the size of the investment adoption of social media demands. Like any ten year old in the back of your SUV on the way to your mountain cabin says; are we there yet?