While I'm pretty sure this Wired bit about "how to avoid a heat seeking missile" is somewhat tounge-in-cheek, it does have some very valid points. It also, however, misses an equal number.

Caveat: I am not a missileer, nor am I a pilot. What follows is what I've gathered through decades of reading military hardware specs (in my spare time, for fun, yes, I'm really that weird), and fighting against these things in various hyper-accurate simulators:

Fun facts you may not know about missiles meant to knock down planes:

• Anti-air missiles, at least the sort that terrorists would use to take a shot at airliners (called "manpads"), are primarily designed to destroy helicopters and single-seat fighters. They have relatively small warheads, usually less than 60 pounds worth of explosives. Compare this with the "small" 500 pound bombs normally used to plink tanks and the "large" 2000 pound bombs used to knock down bridges.
• Manpads are designed to work in comparatively narrow launch envelopes, and are quite limited in range. Even the nasty ones are limited to about a two miles, but are usually really effective at only half that distance.
• While this may seem an awfully long distance, it's important to remember modern jetliners actually move pretty fast, and cover that fairly rapidly even at normal speeds. It also means airliners are vulnerable to these things only during takeoff and landing, very close to the airport.
• As noted above, these missiles are designed to neutralize comparatively small targets. That's neutralize, not destroy. While nasty indeed against helicopters, it's quite common for even small fighters to fly home after being hit with one of these things.
• A jetliner, being several orders of magnitude larger than a fighter, is much more likely to simply absorb the damage one of these systems does and keep going, at least long enough to make an emergency landing.

Are manpads still a danger to airliners? Absolutely. An airplane is not a tank, it is light and finely engineered and not good at being bounced around or having holes punched in it. However, a large civil airliner is probably one of the aircraft most likely to survive an encounter with a manpad.

Bottom line: yes, they're a threat, but not a big enough one to keep me from flying.