I'm definitely stretching this hypothesis via circumstantial evidence, but I honestly believe Pacther may have gotten one thing right: third parties are afraid of Nintendo. They've spent the last few years investing heavily in 360/PS3 infrastructure, with physics engines, graphics engines, and 2+ year long development cycles. They've done an awesome job of completely ignoring the Wii so far.
Furthermore, the market the Wii provides is new to them. They don't necessarily understand it -- they understand what geeky 21 year old males like me want, but they simply have no clue how to adapt games for 10 year old girls or 60 year old men or 35 year old soccer moms.
In short, many companies likely have a ton of time and money invested in "traditional" game development on the PS3/360, and even though most are (at best) treading financial water, their initial investments coupled with their uncertainty about how to even begin approaching the markets the Wii provides have paralyzed them. Rather than adapt, they're going to stick to what they know how to do it, whether it's financially savvy or not.
Again, I'm not saying my conclusions are necessarily correct (They are simply deductions from the way CEO's like Rousen have spoken), nor am I saying that all CEOs think this way (some companies do seem to be embracing the Wii), nor do I think he's right. I'm just saying -- some important people are clearly thinking this way, and wrong or not, it means less games for the Wii than it may otherwise deserve based on its financial strength and marketshare.