i know strategies that are profitable everyday but 1-3 million per day? there's only a few firms that could have done that and they had to pay for flow
you know people that went from poker to trading? i only know people that went the other way. backgammon and bridge to trading options I have heard of though
you used to be able to see last trade size and compare it to what was shown in the dom. so if the bid was 89.29 for 5 and you saw 14@89.29 trade and still 89.29 for 5 theres probably an order there. Of course, this is all automated now