Ars Technica - Why complaints about Valve's Portal 2 ARG miss the point.
As the "main" game progressed, the titles in the Potato Sack were updated with new levels and content. If you were able to finish that content you earned Potatoes that were used to move the whole thing along. The thing is, the new content was all Portal themed, and gave new life to games people may have already finished. In a world where people are used to paying real money for new content for their games, these developers were giving away new content for free.

MCV - Give 'em an inch.
But there's no escaping the fact that some of you, and some of the wider gaming public, are – for want of a more eloquent description – morons. Last month we had to shut down comments on MCVuk.com because of this very phenomenon. A tragic and feeble few were ruining the fun for the decent and noble many.