[Note: I work at Facebook, and have worked on some of the friend suggestion tools.]
There seems to be some confusion about how friend suggestions work, and we definitely want to people to understand how their information is used and their options to control it.
Generally, the contact importing tools and resulting friend suggestions have been used by millions of people to make hundreds of millions of friend connections. We're proud of this (since it is clear that real connections are made) but also understand that people should have control. That's why we include a notice in the contact sync (on phones) and upload (on the web) flows that makes it clear that contacts you import may be used generate friend suggestions for you and others. If you're concerned about being suggested as a friend to others based on the contacts in your address book, you can either not upload it, or if you have already uploaded it, you can remove your uploaded contacts (http://www.facebook.com/contact_importer/remove_uploads.php). You can also block any individual people. These steps prevent what the Alex (or rather, his friends) experienced — people being suggested as friends based on having a phone number in their address book.
Also, some of you have noticed that we don't always require a phone verification for an account. This is a security feature designed to prevent spam and fake accounts that is only triggered when certain conditions aren't met.
There seems to be some confusion about how friend suggestions work, and we definitely want to people to understand how their information is used and their options to control it.
Generally, the contact importing tools and resulting friend suggestions have been used by millions of people to make hundreds of millions of friend connections. We're proud of this (since it is clear that real connections are made) but also understand that people should have control. That's why we include a notice in the contact sync (on phones) and upload (on the web) flows that makes it clear that contacts you import may be used generate friend suggestions for you and others. If you're concerned about being suggested as a friend to others based on the contacts in your address book, you can either not upload it, or if you have already uploaded it, you can remove your uploaded contacts (http://www.facebook.com/contact_importer/remove_uploads.php). You can also block any individual people. These steps prevent what the Alex (or rather, his friends) experienced — people being suggested as friends based on having a phone number in their address book.
Also, some of you have noticed that we don't always require a phone verification for an account. This is a security feature designed to prevent spam and fake accounts that is only triggered when certain conditions aren't met.