On a serious note...If i was to have a guess at the reasons...

On a serious note...If i was to have a guess at the reasons behind todays dip I would point to
The Reserve Banks interest rate decision today (rates on hold at 1.5%) depends on who you listen to

Financial review are saying its gonna cost business higher wages because RBA noted a skill shortage.
http://www.copyright link/news/econ...towards-an-interest-rate-rise-20171205-gzz561

Then you have Business Insiders overall picture Seems like most economist think RBA will not lift interest rate for a while.
https://www.*.com.au/rba-interest-rate-decision-economists-react-2017-12

Then like you say the old Amazon bandwagon hit town... so I suppose a bit of money followed that around

And Lastly ALL the Big Banks are getting hosed...because of the Royal Commssion being drafted up. A double whammy for banking sector Interest rate stagnation and the Feds about to crawl up their ass
Pretty much got them spooked, Blue Chip investors are fearing the END OF THE WORLD and then in a day or two they will calm down and put the cash back in to the market.

Over here in the penny stock division we deal with the End Of The World scenarios on a Daily basis so a Royal Commission or Interest rates up/down/sideways hardly rates a mention.

Just a bit of my personal overview...I sure its one of those reasons.