I just point it out as suspicious so that the problem setter (or an admin) can, if they want, look into it and see if submissions match official solutions or some other form of cheating. The user had some trouble with much easier problems (such as PRIME1), based on profile and recent submissions. He also submitted several NWERC 2011 solutions right afterward in the same fashion. So a number of factors make it look strange.
In the end though, I feel like even pointing out such things is maybe a waste of time. Could be spending the time solving problems or other interesting things. People wanting to cheat will always exist, and they won't gain very much from cheating, and the points/ranking dilution is generally not very extreme anyway..