A billion-plus dollar pre-IPO tech start-up (or unicorn) was, only a few years ago, something of a myth.

Now, however, unicorns seem to be popping up everywhere including fashion (Farfetch has just raised $86 million valuing the company at $1 billion).

In 2013 there were 38 tech unicorns is total, today there are more than 80!

But some have voiced concerns that the growing number of unicorns may be indicative of a second dot-com bubble – especially since a fairly high percentage of them are yet to generate revenue, yet alone profit.

So why are there so many of them? And should we be worried?

Last week it was rumoured that Amazon, the online retail giant, was involved in ongoing talks with London-based luxury fashion retailer Net-a-Porter (thought to be worth around 2.5 billion euros) to discuss the possibility of purchasing it.

These rumours were quickly quashed. And now it has emerged that Italian clothing and accessories company Yoox is going to merge with the British fashion retailer instead.

So where did the Amazon rumours come from? And what does the future hold for Net-a-Porter?