If one link list has a recip with 15 links on it, and the rest of the recips in your table have 2 (index and cat pages) then it is unfair on the other LL owners. Say on a free site you have 9 recips (x2 links each), + 3 sponsor links, enter link and a link in the footer to your index page - that is a total of 23 links on the page, of which the link list owners all share equally of the incoming page rank (minus dampening factor) to that page.
If one LL tries to seize the lions share with a 15 link recip then they are taking a disproportionate amount of PR, especially when you consider that you get more linking benefit from a larger authority LL than a small one. Not only is it unfair on the other LL owners, but it also totally cuts down on the residual trickle down PR effect for the free site builder - there might not be much PR left after the recips have filtered off their share, but the effect can be significant over tons of pages... but not so much with 15 link recips. Now I realise that PR is not so cut and dried any more but it's still clear that all G really cares about is links... JMHO of course.
