Not sure if it's a scam, but I bought some cheap XRB there a while ago. I was trying to log in just now, and apparently their website has vanished completely. 
Their stats on CoinMarketCap also haven't updated for 3 hours. I'm willing to accept my losses, but if someone is actually able to reach their site, please post below.
As shitty as an exchange Mercatox is (and boy, is it shitty, I have had deposits "vanish" and they ended up not being credited to my account), I don't believe they are a scam (or at least I hope not, who knows).Their stats on CoinMarketCap also haven't updated for 3 hours. I'm willing to accept my losses, but if someone is actually able to reach their site, please post below.
They disabled their website due to a large DDoS, see https://twitter.com/MercatoxCom/status/948143881467645954