Yes, it can be. Brokers known as 'Market Makers' initially take the other side of their clients trades and can, if they want to hold on to the position and effectively bet against their clients.
However there are actually some advantages of trading with Market Makers too, but in my opinion not enough to out-weight the benefits of trading with a true level 2 DMA broker.
I have a short article on the two different CFD broker models here:
CFD Providers