Nevol,
An additional thought - just looking at the number sweeps people enter doesn't give enough of the picture. Same thing for the number of years people have been entering. I am very selective and don't win often, but I have had a handful of wins which made me very happy...not mega wins, as some people are fortunate to receive.
So, beyond the numbers, I think it may help to look at what you are entering. I could easily enter hundreds of dailies and one-entries which I choose to pass up. Sometimes I really would like to win the prizes, but I have never seen winners from certain sweeps. I hope the people who continue to enter them faithfully will post wins someday...but if you are entering that type of sweep, your chances may be slim. Other kinds of sweeps, like magazine dailies, seem to be hard to win from, but I have won from them a few times. Still, for the number of entries I put in, it seems like a small return.
On the other hand, there are some sweeps that offer lots of prizes, and daily prizes. I think chances of winning may be better with those. Same thing with sweeps that are short run. If there are only a few days for anyone to enter, then there should be fewer entrants, right?
Some people do very well on instant wins, but others don't. You may want to give them a try, if you aren't already entering. Again, some offer many prizes and will have many winners, while others may run for a long time and offer very few prizes, or small prizes like music downloads. Still, you get a winning screen or email, so you did win.
Many people do well on blogs and social networks. It is all a matter of personal choice and style, but you may want to look at what you are doing and try a new approach.
If you continue to enter regularly, you should win something. Let us know when you do!