Shares in North American online retail phenomenon Amazon.com hit another record high overnight of US$726 per share to give the company a market value around US$344 billion.

That means it’s now bigger than Facebook Inc. and has almost the same market value as Warren Buffett’s investment conglomerate Berkshire Hathaway. Amazon is now reportedly the sixth most valuable company in the US with only the likes of Google owner Alphabet Inc, Apple and Microsoft ahead of it.

Amazon is an excellent example of the rapid growth of the digital economy with its shares being the number one performer from the US S&P/500 Index in 2015 and returning nearly 2,000% to investors since 2006. Moreover, some investors expect that it could go on to be the first $1 trillion company in the world.

If it does keep growing quickly investors in traditional bricks-and-mortar retailers in Australia like Myer Holdings Ltd (ASX: MYR) or (now privately held) David Jones would be well served to stay cognisant of the online risks coming from overseas retailers. Other online-only overseas retailers growing rapidly in the digital space include Chinese giant Alibaba, US-based Hypebeast.com and UK-based Asos.com.

Another one of the top-10 performing shares in 2015 among the flagship  S&P/500 Index was online travel booking giant Expedia Inc. The US$16 billion travel group delivered a share price rise of around 47% in 2015, which was mainly driven by bookings growth that allowed it to outperform almost every other large-cap company it competes against.

The online-only travel agent is up 325% over the past five years and its US and global success is another reason why some commentators remain bearish on the outlook for global bricks-and-mortar operators like Flight Centre Travel Group Ltd (ASX: FLT).

Elsewhere the S&P 500 Index’s best performing stock in 2015 was online broadcaster Netflix, which returned around 147% in 2015 and has climbed more than 700% since 2012! Needless to say its popularity amongst the youth market in particular could spell long-term trouble for Australia’s free-to-air broadcasters like Ten Network Holdings Limited (ASX: TEN) and Nine Entertainment Co Holdings Ltd (ASX: NEC). They are down 55% and 43% respectively over just the past year.

Evidently the growth of the digital economy is one trend smart investors should not miss out on.

For ASX investors probably my favourite stock in this space is property website operator REA Group Limited (ASX: REA), with global growth horizons and a return on equity of 36% the shares look a buy at $55.10. Others with long-term potential and attractive economics in this space include SEEK Limited (ASX: SEK) and Carsales.com Ltd (ASX: CAR).

While investors prepared to take on more risk in search of the digital hit of tomorrow could consider online jobs portal Freelancer Ltd (ASX: FLN). Its shares sell for $1.52 and it remains an on a reasonable valuation relative to its outlook.

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Motley Fool contributor Tom Richardson owns shares in REA Group.

You can find Tom on Twitter @tommyr345

The Motley Fool Australia has no position in any of the stocks mentioned. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy. This article contains general investment advice only (under AFSL 400691). Authorised by Bruce Jackson.