I've just made a very mundane purchase on Amazon and at the end I had the opportunity to 'share' my purchase on Facebook and Twitter. Why would anyone want to 'share' it, I've not bought a diamond necklace or a Maserati!
Because they've realised that some people will tell the world about anything they do and it's all advertising for them. Plus why complicate the code on the page by trying to decide if this is a purchase 'worthy' of being shared :-)
Agree completely. But "keeping up with the Jones" is more rife than ever amongst the younger generations today, so such sharing is a very persuasive marketing tool. Peer pressure predominates.