Facebook and The Blair Witch Project?

Second the Twitter inclusion –

http://twitter.com/GordonM

Clearly I am just adding these as when they pop into my head .. but here’s another … Primark.

I second Facebook – the buzz was pretty high, but I got converted in the traditional viral route – someone posted photos I wanted to see, so I joined for a single functional benefit, then discovered online Scrabble, and now would die without it.
Another idea would be innocent drinks: I got into them because I noticed people reading the labels in the shops and giggling. They used the labels to create buzz. They’ve been Web 2.0 since before the phrase was invented!

Zattoo

North Face jackets … they started being worn by trendy urbanites … then became the preferred look of BBC reporters & are now everywhere … never has an item of outdoor apparel spready so quickly