Amazon probably qualifies. eBay, sure. iTunes (sort of; arguably, the hardware drove everyone to iTunes originally, and the hardware was not cheap to produce or bring to market; but once the install base became stable, it grew VERY quickly through word of mouth).
Also: a high viral coefficient does not necessary = social, even though that's what people assume these days. I think the world has seen way too many businesses in recent years that are "social" for no other reason than that social is supposed to have magical network effects. The reality is that not every product, experience, or piece of content is truly social by nature. Trying to tack social onto a use case that doesn't support it is not going to yield a viral coefficient.