I had the good luck to share a cab back to the airport with Wez Furlong after php|works. Wez had presented a new talk about how to work with email properly (jokingly subtitled "Not PDO" by everyone there), and was curious to know how it was received. I replied that I liked it, but struggled for a moment on "why" ... and then it hit me: the reason I liked it was that it was about a fundamental operation that still seems to trip developers up regularly.
Although I told Cal Evans when he interviewed me that the next technology I'm really interested in is AJAX (particularly its implementation in Protaculous), I'm not as excited by it as everyone else seems to be. I think it's neat, but good grief, if wide swaths of developers can't do input filtering properly, what good can adding AJAX do? Get the basics right first, then you can do progressive enhancement as you go.