The decentralized nature of online conversations often makes it easier to manipulate public opinion, both domestically and globally. Regimes that once relied on centralized systems of media control can now deliver ideological messages more subtly, with the help of little-known intermediaries like anonymous commenters on websites.

We've never thought too deeply about the roles things like forgetting or partisanship or inefficiency or ambiguity or hypocrisy play in our political or social life. It's been impossible to get rid of them, so we took them for granted, and we kind of thought, naively, that they're always the enemy.

The Egyptian experience suggests that social media can greatly accelerate the death of already dying authoritarian regimes.

In the past it would take you weeks, if not months, to identify how Iranian activists connect to each other. Now you know how they connect to each other by looking at their Facebook page. KGB ... used to torture in order to get this data.

It's true that virtually all new technologies do trigger what sociologists would call 'moral panics,' that there are a lot of people who are concerned with the possible political and social consequences, and that this has been true throughout the ages.

The great temptation of Big Data is that we can stop worrying about comprehension and focus on preventive action instead. Instead of wasting precious public resources on understanding the 'why' - i.e., exploring the reasons as to why terrorists become terrorists - one can focus on predicting the 'when' so that a timely intervention could be made.

Personalization can be very useful in some contexts but very harmful in others. Searching for pizza online, it's probably OK to keep showing the same pizza shop as your No. 1 choice. I don't see any big political consequences out of that.