I just joined the Chess.com community and I'm amazed at how many features the site has. It is without a doubt the most comprehensive tool to improving your chess skills that I can find on the internet.
That being said, many of those same great features are not open to free members or (even worse) severly limited. Take Tactics Trainer for example. Free members can only do 3 problems per day, far from the practice needed to acheive tactical mastery. Even Gold Members have a limit of 25 problems a day! It isn't until Diamond or Platinum that players are given unlimited problems. Yet Chess.com claims that "Chess is 99% tactics..." It is, but Chess.com doesn't offer the training needed to master that 99%.
Although I understand that the site has to make a profit, from the use of ads and constant messages to members' inboxes encouraging them to upgrade or visit the shop, I'm not convinced that the membership level system is a complete necessity.
Chess.com does offer many features, but the limitations that come with being a free member are probably driving away more business then they are attracting. For example, I do most of my tactics on Chess Tempo, which also has a paid membership system, but all members are able to do unlimited tactics. The only features that have a price tag on them are the ones that you could do without (for example, creating groups of problems that you miss the most, mates in 1, 2, 3, and 4, having unlimited endgame problems, etc.)
Long story short, I think that Chess.com could attract more web traffic by reducing limitations on free members and making sure that premium features are actually not required to improving a player's chess.