I don't know what it means, but an addition to "Possible reason 2". If everybody will withdrawn there BTC from Bitfinex, Bitfinex will be forced to sell ETH for BTC to have enougth and this will bring ETH price down. And I am long on ETH. So bad news..

And here is a BTC Autflow chart: https://blockchain.info/de/charts/balance?address=35emx395afKAKAr72VoePVbu3FJvxLPVny&timespan=30days