Regardless of which number we choose, to extend flash memory's ability to work without errors, manufacturers must implement a wear-leveling strategy -- in essence, distributing writes across cells so that no cell will be forced to an early failure.
If you are interested in learning more about wear-leveling algorithms, this presentation in PDF format from a university in Taiwan is useful, and in English.
But the question remains, is Hagberg right about SSDs? In a word, no, although he does raise some good points. However, I don't think that the clash between wear-leveling and RAID creates an insurmountable problem. For example, this vendor has been offering a RAID card that mounts flash SSD (PDF file) for quite some time.
Nevertheless, at the current state, many customers will probably agree that SSD can be a little pricey for their taste. But there is a range of customers that will appreciate the additional performance and will gladly pay a premium to get it. After all, many people travel first class, and they love it.