A lot of the people I know who don't have office jobs say they never get real email any more - only newsletters and pings from the social networks they use. This new graph from Hitwise tells a similar story and perhaps the beginning of the end for email as the main way people message eachother on PCs. That social networks are being used more than email.
The Hitwise stats can sometimes be misleading. For example, one visit to a webmail site like Gmail.com you could send and receive 20 mails. And one visit to Bebo and you might just look at pics. But the message is clear and the impact on marketing and PR continues to gain strength - emails get ignored a lot of the time as people move to different places.