While sat in the Crucible Theatre I noticed that certain seats have a gold plaque on them with either the name of a person or a company name attached to the seat. Some seats don't have any. What does this mean? Does this mean that the have sponsored that seat?

I've watched the odd bit of snooker from the Crucible on TV and just about every time I've noticed that there seem to be plenty of spare seats.

Is this because people who bought tickets have not bothered to run up? Or is it that they've not sold?

No it's because corporate seats are bought up for people who aren't neccesarily that interested in snooker, and sometimes they can't be bothered to turn up for the full game. Or sometimes they just spend the whole trip in the bar or other bars in the city, enjoying their free accomodation.

From memory when the Crucible was first build some of the money was from the general public fund, raising like buy a brick/sponsor a seat etc