Poker is evolving. Five years ago, the games were much different than they are right now: much looser, more action, less educated players. With the advent of online poker, poker as a whole has exploded and so has the amount of poker information.
There are numerous books, videos, seminars, websites, etc. Even this site educates players on how to play better. Also, you have a big rush of younger players coming into the games who do their homework. What this means for the games is that since a large percentage of the players know decent strategy, it is harder to get good value on big hands. You have to always ask yourself, how do I expect to beat a game? If everyone sees that I'm play tight, how am I going to get action on my big hands?
Continued Evolution of the Poker Games
This is where deception comes in. I think that as poker continues to evolve, the players that are going to do well are the ones that will be able to create a veil of deception, which forces other good players to have to call down with weaker hands.
What is deception in poker? Deception is playing a hand in a way that isn't the ideal way of playing it. The two ways of that are to either bet a hand aggressively that doesn't deserve it, or to call with a hand that deserves raising with -- either slow playing or over betting, basically. Since you aren't playing a hand ideally, there is an inherent cost. You are either taking on extra risk or you are giving up some money. The reason this is both necessary and beneficial is because of the effect it has on future hands. The goal is to simply create an environment in which you can win. You are essentially drawing good players out of their shell and forcing them to battle with you some in hands where they are out of position, and don't have strong holdings. See, even if you just break even on these plays, it adds a tremendous edge to your game since when you do have a big hand, chances are you'll get lots of action.
Now, even if you are at a table full of unthinking, uneducated players, they can still spot a rock. It doesn't take a rocket scientist to spot someone who isn't playing many hands and when does, usually has a big hand. This is why deception is key to winning, even if you play a tight game.