I can see one advantage, albeit in limited usage. For non-branded searches, host crowding is a tremendous advantage if a person has SEOd enough to show up for two positions on page one.
For example, if brandx was showing for money term in position 1 and position 10, they now appear in position one and two. This is a tremendous advantage for a "marginal" result (the position 10 result)
However that's the only reasonable reason I can see to remove it.
I agree that MC does seem to prefer it, and infers that nefarious SEOs would try and hack it to get around the system. In other words, the "hacker" would prefer a lack of host crowding. If he views that as hacking the results page then clearly the current state of affairs is less desirable from the user experience.
A follow on question may be warranted. Why would Google want this? It doesn't seem to be the preferred case for MC, it doesn't practically seem to increase result diversity, and there's in implication that host crowding was better fro the user. So why do it, save the edge case of "snapping" a second result up to the top?