The following got me thinking:
Shipley and Schwalbe argue that in the internet age, a dash of sensation is just what is needed. "Email is without affect," they write. "It has a dulling quality that almost necessitates kicking everything up a notch just to bring it to where it would normally be."
Hence the profusion of exclamation marks. Stuart Jeffries (who wrote the article) takes issue with the post-rationalising theories of Shipley and Schwalbe – but the idea of an exclamation mark arms race does seem to ring true.
It reminded me, in fact, of compression in recorded music – the process whereby dynamic contrasts of loud and soft are ironed out in favour of a uniform loudness. I've written about this – in the context of a record review – on Heavy Soil.
In the case of both the email exclamation mark and the record producer's compression processor, there's that idea of making something a bit larger than life, a bit more 'real', a bit more punchy, a bit 'louder'.
And all it does is make everyone else do the same, for fear of seeming insipid/lifeless/quiet.
Anyhow. I urge you to read the whole article. It's funny – and clever.