Re: Coinbase just told me I'm not eligible to purchase BTC. Because the price is up?
Had several cash deposits and withdrawals in the thousands combined with activity from "coinbase.com." I found the magic recipe for getting your bank account closed 
You were buying btc, so why did you have cash depots AND withdraw at the same time? Large cash amounts like this trigger money laundering to the banks. If they cannot follow you money other than coinbase transaction, they'll just close your account just to be on the safe side.
I had large cash withdrawals as well because I would also purchase BTC directly from miners by depositing cash into their bank accounts. Definitely way too much cash flowing in and out and it got flagged. They never give a direct reason. All three banks just gave a similar rendition of: "We no longer deem it mutually beneficial to maintain a relationship with you."