In a fuzzy little nutshell, they attempted to sell their product (PageRank algorithm) to the search companies of the day but got no takers. After "failing" to

In a fuzzy little nutshell, they attempted to sell their product (PageRank algorithm) to the search companies of the day but got no takers. After "failing" to cash out, they took their confidence in what they had and built it into a public service. Initially, I think they were dead set on not subsidizing their site with advertisements and were definitely not thinking of doing subscriptions or anything of that sort. In the end, I guess they simply weighed the alternatives (i.e. closing the doors and finishing their PHD studies) and figured that instituting any sort of sustainable business model is not so evil after all. Good for them (and us). :)