Rushing to the IMAX to see How to Train Your Dragon turned out not to be such a clever idea. Getting good seats in an IMAX is, IMHO, essential, but the cinema was pretty empty so there was no need. Wouldn't it be great, I thought, if there was some (Twitter supported?) service to let me know: no need to rush, plenty of seats. However, it is not clear that the cinema wants you to know this and, by definition, if there are few people there, the chance of the information being volunteered is slight.
So, why we are all thinking of a ubiquitous information future, there are likely to be (many?) situations in which there is no economic or social reason for the presence of that information.