A large percentage of people who rush out to buy games at full price do so knowing that they can sell the copies used to get back a good portion of the purchase price(within a few months of release), since used copies will no longer be as functional they'll most likely lose a good portion of their value much sooner. When people will stop wanting to buy used copies and these customers find that their recent games are worthless, they might be discouraged from purchasing new games at full price. Where do all these game stores get used copies to resell? People trade them in for credit, and if they won't be getting a decent amount for them they'll stop buying them at full price. Either way the companies will lose money, either they sell fewer copies for more money or they'll sell more copies for less money.
Also, how much would they really be losing by keeping online play available to those who purchased used copies? Plenty of businesses that deal with online services go with the "Freemium" business model and it works for them.
http://www.wired.com/techbiz/it/maga...urrentPage=all
True, but consumers can still complain about it. Before people could buy a used game and it would work just as well as a new copy, now they'll be forced to buy a new copy to use the same features. Of course they can still choose to avoid buying a copy at all, but it would still be annoying to them that they'd have to choose. It pretty much will force people to adopt new systems and purchase new games right away, if a person wants to get a system several years after release and a game that came out several years ago, finding a new copy of that game can be difficult.
I don't really see why they would need to worry about used sales. Books are available used. Even though there are several books that have been in print for over 100 years and are easily available used, they're still in print today which means there's still enough people wanting new copies. Just make a game really good and enough copies will sell. Imagine if used cars were banned to increase auto sales, how many people could still afford to own one? Would more people buy new cars or would less people own cars?