I dont think the root cause of issues is the number of people, but rather that the current system is vulnerable to manipulation.
Yes, probably. Finding some logic to fix this issue you mention would be much harder than limiting the size of the list. Just favoring the one with most votes won't do it, much less so the one with the older account.
Or we get a hybrid system.
I like it! This might actually work: force users to choose:
Option 1: Use theymos' DT1 selections and use the system as it was last year.
Option 2: Set your own custom Trust list and use the system we have now.
That could be an option, except newbies would be basically choosing at random.
But really what I meant with a hybrid system is mainly the current system plus a black list plus a white list.
So some users would always be on DT1 (unless theymos removes them, as with the old system), others would never be there (regardless of how many votes) and all the others would depend on votes. More factors could be added too.
Edit: Maybe it would help adding some obscurity or hidden randomness to the system, so it's more difficult to manipulate it by adding someone knowing that will have desired effects. We should add people whose feedback (and the feedback left by users added by him) we trust and that's all. Maybe we shouldn't know every detail of the whole system.