FaceTime had gone missing in parts of the world, mostly around the Middle East. @dutweets is the official Twitter account for du, the telecom operator for the iPhone in the United Arab Emirates, and in a tweet just a little while ago, the account confirmed that FaceTime is currently unavailable in that country. The iPhone hasn't even officially launched there yet, but the account also says that FaceTime "won't be working as of the launch" (which takes place tomorrow), so even official customers there won't have access to the video chat feature.
Unfortunately, there's no detail yet on why -- we've heard that there may be local restrictions on VoIP technology that would block these kinds of communications. And this is only confirmation for the UAE, though it's probably a pretty good guess that other outages are legit as well. Stay tuned -- we'll keep an eye out for official confirmation in other areas, as well as a reason why this decision was made.
Update: The Next Web Middle East has a confusing writeup that suggests Apple pulled FaceTime because it was assumed assumed the feature would run afoul of the region's regulations around VoIP. The suggestion is that Apple made this move unilaterally, without consulting the carriers.
Update 2: We have a report from a Saudi Arabian source that FaceTime is working in the kingdom. However, subsequent reports show that once the iPhones are updated from the shipping iOS version, 4.02, to the current 4.1 version, the FaceTime feature drops away.