I would agree with your external link theory IF the anchor text of the outbound links was spammy or repetitive.
Red Widgets . . .
yada yada yada
Blue Widgets . . .
yada yada yada
White Widgets . . .
I've seen one of those social bookmarking sites with 950d pages and many of them have user-created anchor text.
The users, of course, the general public, not surprisingly, take no consideration of possible penalties when choosing the titles or links.
Since related external links are grouped on the same page, it's inevitable that the pages are going to get extremely spammy anchor text.
One of my competitors has a forum which regularly posts new content from users, and it's set up to allow the users to create the anchor text (like many forums). There is so much repetition because the webmaster has surrendered control of the site to visitors, it remains below my site in rankings.
(This is one reason why I decided not to add a forum to my site.)
Incidentally, on the subject of the 950, I only just noticed in mid-December I recovered from a 950 penalty on one phrase I'd not realized I'd been penalized for...
There are so many phrases related to my sector, I can hardly keep track of them. So my solution (a project I started in early December) is to remove all repetitive anchor text on the same pages sidewide.
Other sites may get away with the repetition, but I probably don't have enough inbound links to satisfy the Google Algo repeats on my site are justified.