Confused about Facebook iframes

I am a little confused about Facebook's switch to iframes.

I understand the iframes are so much more powerful, but isn't that the problem? Don't iframes give people the power to turn Facebook into an ugly spam-o-rama of affiliate pages?

I don't understand why Facebook would open itself up to that.

Especially since it must know what happened at Squidoo 4 years ago...

I know this is eons ago in internet time but doesn't anyone remember the "Squidoo slap" of 4 years ago? Squidoo allowed iframes so a bunch of real low-life marketers started throwing up a tidal wave of super spammy pay-dot-com affiliate pages. Finally Google decided that Squidoo pages were too spammy to show in searches. Then all Squidoo pages dropped down or disappeared from Google search results. Squidoo immediately cleaned up its act and banned iframes. But it never completely recovered its favored status.

What I don't understand is why Facebook would open itself up to that kind of abuse. There must be someone over there old enough to remember what happened at Squidoo 4 years ago. Why don't they worry that this will happen to them?

Also they saw MySpace turn into an ugly ghetto of trash because users had the power to completely customize their pages... Why is Facebook looking to go down that road?

I don't get it. In the wrong hands, iframes just seem like such a license to build garbage.