Diminishing earnings over time

I've been playing online for approximately 9 months, butI do my homework and work at it, so I am actually showing a slight profit, about $12/hour in 2/4 and 3/6 ring games. What I have noticed is that I am much more profitable in the first 2-3 moonths on a site, then begin to take a ton of bad beats, usually in the larger pots. This has happened on Empire (two separate runs)and Full Tilt. I was $650 up on Empire for July-Sept, and then dropped to $150 in the first week of Oct, everything that could go wrong did. I moved to Bodog, and have been winning consistantly since. Am I just going through slumps or is it possible that somehow the sites recognize that I haven't made a deposit for a while, and target me? I understand I am playing low-limit and find it hard to believe that the sites really care about my measley cash flow, but I just wonder if others have noticed this trend in their play?