It seems that we have ongoing and dramatic price changes in bitcoin, and surely, there are frequently going to be attempts by larger players to push the price more in the direction of whatever motion that it has, so your above reference to the mid-September price correction down from $4,980 to $2,970 did likely cause panic amongst quite a few people to sell lower than they bought (also known as shaking weak hands). So, there can be some purpose involved to push the market lower than expectations in order to get more folks to sell and to continue to cause further negative BTC price movements.
I think that this particular thread serves a very useful purpose to put some of the ups and downs into perspective because we get to see an ongoing representation of daily weighted BTC price averages, and also, we have just seen stupendous BTC price performance for over a year...
Remember that dooglus was out of a job for almost three years, in respect to this thread,
https://bitcointalksearch.org/topic/m.17282105
and surely expanding from top 20 to top 50 is going to help his job security (which has been a real great perk for the rest of us to be able to see these ongoing posts), but it also just remains fascinating to see that there has been so much persistence of upwards BTC price pressures throughout 2017 - and represented by ongoing posting in this thread for almost every day of the whole year - which seems to show a kind of ongoing bitcoin strength, in spite of several pretty decently sized price corrections (for example, we had four price corrections of 27% or more between September and December)... but the BTC price has remained decently strong throughout and throughout the addition of new postings in the top 50.