That does not stand to reason at all.
I respect your opinion, especially in the absence of an explanation by Google. My argument: Sites that have done extremely well over the past 12 months in terms of increased google traffic (such as ebay and amazon) have many affiliate links pointing to them (mostly nofollow, mostly through a redirect page) while conversely a lot of their affiliates report less traffic. You could debate on that being because of the affiliate nature of the links but the fact remains they are nofollow and shouldn't have played a role. You'd expect this to happen if nofollow was all of a sudden selectively obeyed.
Elsewhere: Matt Cutts recently asked if noindex should also be selectively obeyed. To me that makes their mysterious 2011 "nofollow change" all the more interesting, given the above.
Not really, nofollow is a Google only attribute and adding nofollow to all outgoing links effectively shields me from harm to my Google rankings. My visitors don't care either way if a link is follow or nofollow and this way I would not care anymore either.
besides - the internet 'currency' is shifting from backlinks to social signals and reputation anyway. Why not protect my reputation in the eyes of a computer algorithm by making 99% of outgoing links nofollow? (serious question, has anyone done it recently?)
8000 links are spread over 3500 pages, it's not a directory, I tend to write a lot and any given article may have 2-5 links as examples or sources.
edit: If I asked Matt Cutts I'm sure he would say that it's better to vouch for my outgoing links by not using nofollow on them, it's supposed to be a glove over links to less trustworthy sites and/or a way to protect yourself from paid link suspicions, but since I can't see what GOOGLE thinks is a trustworthy site (and Google is suspicious by nature) I'm bound to get some wrong (and with 8000 have lots change).
My question to Matt now would be: Has Google finished lowering the value of backlinks and increasing the value of social reputation yet? I'd love for backlinks and PR and nofollow to be retired from the 'important factor' list to make this a moot issue. Reason: My visitors don't see this stuff much less care.