The porn business is high-margin low-volume, very competitive and has a low turnaround time. This forces it to be extremely responsive to even subtle undercurrents in the mood of its customer base.
Conjecture: The set of popular textual advertisement themes for porn (e.g. subject lines of porn spam) undergoes systematic collective fluctuations. (New popular themes arise and disappear) These fluctuations contain a nontrivial signal about the current zeitgeist among the primary target audience (suitably subsection the audience if there is enough breadth in the market to justify so doing) and could be usefully mined for a lot of interesting information about what’s going on in the country. Its fast response time makes it particularly interesting.
This could be a better signal than e.g. tabloid covers, since while they have similar fluctuation patterns, they seem to have settled down into a fairly constant set of themes that doesn’t fluctuate nearly as broadly as porn.