Ilya Grigorik's post on Collaborative Map-Reduce in the Browser explores how to leverage visitors to do computation. While I think he is looking in the right direction, I don't think he is thinking large enough. Moving your worker code into widgets lets you "leverage viral growth" to do computation.
Why Google bought Youtube
Anytime you see a Youtube embed, your computer is doing computation in the background. Ask a Mac user and they will tell you how hot their computer gets with a single Youtube video. I suspect Google is testing their grid by having Macs compute pi to hundreds of digits. If results are positive, G2C2 (Global Google Compute Cluster) will be activated for everyone.
Computation is serious business
Lowly clients can do some serious work. Bit-torrent uses a variant of Tit for Tat to punish leechers who download without contributing bandwidth to others. Avril Lavigne - Girlfriend's 116 million views could have contributed 838 years of compute time.
Bloggers and social networkers could leverage their reach to help cure cancer. Laughing Squid could embed a wrapped youtube player that folds protein in the background.
