Hmm... I am not 100% sure if there are less player in total, but since amount of xp and gold are based on time - some will naturally prefer a less crowded server, since it opens for more "personal" gameplay, or less chances to get a random bolt to the head. ( i have skipped the last page, so there might be some similar replies )
I personally, take long breaks between games now. I can play for 30 min - do something else, and play for an hour or so later the same day, then take few days away from M&b. And I belive many are doing the same thing.
Some will disagree, but these days - a game without some sort of grind ( gear/skills/achievements/global high-scores/whatever else you might think of ) is not living for a long time. It is like 3D graphics, you expect it from a game. Its a fact. There are simply too many other games. The gameplay alone is holding only for some time, since there are some new titles coming out every day. Every day. ( Monday Night Combat is a blast! And its 10 Euro only. A pizza that i am eating right now costs 14 Euro. )
Same as i did not get married with my first girlfriend when i was 16, to live "til death do us part" - I do not want to stick to the same game, if it does not have any new tricks left. Yes, missionary is the most comfortable and overall best value for your time, but there have to be some more achievements to unlock there...
I might be just bored here, but really, 1 hour of M&B a day - is enough now. Its still fun, but 1 hour is enough.