The newest comics over the past few days discuss power creep in the 4ed game. Power creep is when each product that is released tries to outdo the power level of the products that came before it. After several years of this happening the power level of the original game and the newest books is vastly different. So much so that playing a basic fighter is very unappealing next to whatever cyber ninja monkey warrior that came out in the latest source book.
Power creep was very bad in 3rd edition some of the last source books that were produced had vastly overpowered abilities when compared with basic PHB characters. Another thing about power creep is as the players become more powerful it requires a similar buildup of power from the GM. What you end up with is a role playing arms race.