Evolving, yes expanding, yes declining, no. A combination of the speed of Technology and the snail's pace of Education has meant that at least two whole generations escaped being taught how to write e-mail in school. There are no rules for personal e-mail other than emotional effectiveness. This, plus economic good times, is a familiar recipe for a major burst of cultural energy. As in Elizabethan England 17th Century France or periods of Japanese court history the ability to write witty athletic stand-out short texts is virtually required now for success in business social groups and love.
People are glad for a chance to be proud of their clandestine literary craft.
You just can't tell anybody about it. NOW there are correspondences taking place that will be collected and preserved and published and which we will read and re-read in our last years.