The University of Santa Cruz/California has an interesting demo up that computes author trust based on whether users' edits are kept/improved or reverted. It then highlights passages of the text according to the computed reputation of the author who added them:
http://trust.cse.ucsc.edu/ http://enwiki-trust.cse.ucsc.edu/index.php/Special:Random
NB, this is still very experimental, but it seems promising.
Luca de Alfaro, who did most of this work, will also be presenting at Wikimania.