What's the Difference Between a Lead and a Like?

Our ability to like (and share) information, photo's, articles and interests on the web is fast becoming an online way of life. I remember the days when you used to forward emails (usually 'borderline' jokes) to each other in the hope they would pass it on (no, oh well just me then!).
The resulting data from Facebook and all the other social likes has created an overnight demand for a new army of online data analysts whose job it is to crunch all these numbers into something resembling an accurate picture of consumer preferences and forecast of future intentions. In the US, the term CPL is increasingly taken to mean cost per like (sacrilege, indeed).
But let's not get confused with the real thing, a lead is an insanely valuable piece of information on a consumer that is rarely beaten for accuracy, preference and intention to buy. You've just got to know what to do with these drops of marketing gold-dust fast to turn them into gold-plated customers.