Where is Roku customer support commenting on this strange sequence of events?
Nothing strange about power supplies ceasing function. Roku obviously knows the ps to be a weak point as they make it available as as "accessory"for $10. What should they say? "In order to keep the price below $100, we provide the Roku with a cheap, easily replaced power supply."
I bought my Roku in the first month of its release, and had to replace the ps a couple of months ago, after a series of power failures and surges hit my apt building. The same event fried my PC -- I work at home and had to miss work for a few days, so the sawbuck was the least of my concerns.
If your power supply fails, it's likely due to variables in your house current, unless you keep it on a high-end UPS/surge protector. But even in the best conditions a ps will just plain die of age eventually, and inexpensive power units like the Roku's are not designed for longevity.