Arguing A Bit
I'll just simply say that numbers 1 & 3 are those good old-fashioned (in web terms) 'sticky' tactics; and unless they are related to your product or service you've got little reason to employ them rather than written content which addresses questions & interests which move them to purchasing. I'd bet that the increase in sales the company noted in the first had more to do with information given (via the avatar or other site info) rather than a chatty-Cathy device. In the latter, I wonder if the widget actually detracted from sales.
And number 2 is cost prohibitive for most; although those with small product lists can do this manually (both in terms of creating links and awareness of what customers buy or are likely to buy).
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