I'm 99% sure of a scam. Withdrawals page was down then back up again now but can't withdraw....Can't believe I got stung on this, but lesson learned I guess...

Some key things I found after realising my error:

• BTC address for the sierrahash - quickly dropped from 49BTC to around 8BTC. Got back up to 12, then 4x 1BTC withdrawals to CkCYmVScaJByuKPKr1w8HegyWdAtuV9x7 when no one else could withdraw

• Article claim it was a scam from December 5th (wish I saw this first!): https://www.scambitcoin.com/sierrahash/

• sierrahash registered details from Whois. I found a fuzzy matching search and found that there have been plenty of these before that were registered in Mayfair - London (must be a place for trading houses so good cover). Will be always using data and reputation checker site going forward!

• The Facebook page is closed down and some others are talking about it on Twitter.

• I've tagged the address for being linked to the scam here. Also worth bookmarking!

The lesson learned here is not to buy in to anything like this with your own cash.

Next one of these I see will be a highly promoted post from me with a full review of everything I've found out whilst realising my BTC is gone for good about how they work.