WPMU have done an awesome study into WordPress demographics.
Firstly, they found that 70% of a sample of 1,517 average American citizens have no idea what WordPress is. Which, they say, is great, because it means that actually, 30% do know what it is.
The survey was carried out with Google Consumer Surveys, a tool that claims results are accurate when you use a sample of at least 1,500. More men than women had heard of the platform and the most knowledgeable age range is 35-44 year olds. See the full findings here
Of course, this is a picture of painted of the US. What we're wondering is, how would the UK compare?