I attended the Bruce Clay training at SMX Advanced Seattle, and he mentioned link pruning/sculpting (here's an SEOMoz article about it - http://www.seomoz.org/blog/google-says-yes-you-can-still-sculpt-pagerank-no-you-cant-do-it-with-nofollow)
Now during his presentation he mentioned that if you have one page with multiple links leading to another page, and one of those links is nofollowed, it could cause all links to be nofollowed.
Example:
Page A has 4 links to Page B: 1:followed, 2:followed, 3:nofollowed, 4:followed
The presence of a single nofollow tag would override the 3 followed links and none of them would pass link juice.
Has anyone else encountered this problem, and Is there any evidence to support this? I'm thinking this would make a great experiment.