Why sony has not been "trying" harder - After they "defeated" Toshiba in the format wars, they and their fanbase were so excited, PS3 owners saw this as a victory over the xbox 360 and couldn't wait for Microsoft to shutter the doors on that division. Unfortunately people only bought a few more PS3s following this event and that quickly ended a month later. Sales of bluray have flattened out and Sony hasn't figured out why even though HDTV prices have fallen so much.
The North American Market - Its no secret that the 360 sells better in north america and generally poor in other regions of the world... until this year it seems. While sony has dominated sales between it and the 360 in nearly every other region outside of NA the deep price cuts from MS and the plethora of big titles for the 360 are pulling in the sales. While previously games were made for the japanese market and then exported to NA it is now a different story altogether. Studios are seeing the value of the North American market. More 360s sold worldwide than the PS3 and the fact that 360 owners tend to buy more games than a PS3 user would are all very attractive to the industry. We're a dominating consumer region for games now, just look at all the japanese RPGs being made for the 360 that would once be considered illogical to do. Look at the top selling game for the two consoles: Motorstorm (3mil sold as of dec 07) VS Halo 3 (8mil as of jan 08). High priced games are selling better on the 360.
Its all about the money they have, not could have in 4 years - MS had tens of billions sitting in their savings account up until recently when they decided to buy back their stock and boost dividends to share holders. Sony on the other hand is one broke motherfucker that needs to start paying its bills better. Seriously though, Sony is in financial trouble on a number of fronts and gaming isn't a cash cow for them. When bluray won the playstation forums were flooded with cheers and support for the victory. Many fanboys talked about how by 2012 sony will have sold more consoles than the 360. 2012!?!??!!??! By then sony will have lost so much money that they will have to sell some of their video game IP or just cancel video game studio projects. Not to mention all the other arms of Sony that would need trimming. MS is a very stable financially secure company, even if the 360 fails (which it can't be by too much at this point) they could continue to build on the brand they've built up now and push out a nextgen model later on. Sony would have to seriously think about supporting the PS2, PS3, PSP and the possibility of a PS4 all at the same time with their 10 year lifespans. So either sony bites a cash bullet the size of a skyscraper and losses billions more on PS4 or watches as the 360 takes over the nextgen market even earlier this time around.
The online & the achievements - Sony once said that gamers didn't want to play their consoles games on the internet. Soon after the xbox (original) came out and sony soon announced a modem attachment for the PS2. Rumors swirled around the PS3 having an achievements system. Despite fansites for the console being quite favorable to this they (sony) denied this was coming and claimed gamers didn't want such a feature. I've never seen sony fans so mad at their product maker before. Now sony has added Trophies. Sony is also chastised by their own fans for having weaker online infrastructure and support. I've got friends who have PS3 but they dont' play together for some reason. Microsoft doesn't do right very often by me but their keyboards, mice and 360 are shining examples of how they not only do well but set the bar in that area.
The PS3's and Sony's future are inextricably linked as I see it. Sony would never sell the playstation brand to anyone under any conditions. So if the company fails, the playstation brand will disappear forever. No question in my mind. Recessions hit consumer products hard and sony stuff isn't very cheap. Their other products lack any uniqueness in a market full of clones like PCs, TVs, mp3 players, cell phones, etc so I don't see their sales improving at all for any of their brands. They'll suffer a lot and make loads of cuts, they may even sever some arms but people will lend to them, they're sony and they can probably make it through this in better condition than many others. But a takeover is STILL in the cards I say.