In Argentina, a new tax is about to be approved that will charge profits for holding cryptocurrencies with 15% per year. (Source) This tax applies for everybody that made profits of more than approximately 3.500 USD per year, so everybody that held more than 0,25 BTC in 2017 would be affected.

This tax will be possible to be charged retroactively, but it will come into effect on January 1, 2018. So everybody that sells before that date, will not have to pay the tax for profits that have accumulated until that day.

Even if you don't believe it: Argentines are a significant Bitcoin holder group. A history of restrictive exchange regulations (the last "restrictive" phase lasting from 2011 to 2014/2015) made many people aware of cryptocurrencies. And at least one of the historical Core contributors is an Argentine.

So it's a pretty likely scenario that Argentine holders could move the price a bit. But maybe it's nothing to worry about: They could re-buy at January 1, so they get only charged for profits after that date.