i think its a valid strategy if calculated properly. a player's point pool roughly equates to experience. Experience is a decent indicator of skill. Skill, is a decent indicator of a player's probability of winning. So, a player's points are an indicator of their likelihood of winning. Since only one player can win (assuming draws are not wins), a player with a lower win-chance can increase his/her chance of winning by ensuring the elimination of players with higher win-chances. So, if you want to win, eliminating the guy/gal with the highest point total seems like a pretty decent idea.
however, note that each indicator is not in exact correspondence with the attribute of which it is an indicator. because correlations multiply and the point shown are not the point pool, the actual correspondence between points shown and win chance is not as great as one would initially suppose.
also, points are not accumulated only through winning. They are accumulated through draws and survivals as well. So, the assumption that high points means high win rate, is actually quite faulty. Points only indicate that a player is good at not losing.
Therefore, because the calculations are based on an 'incomplete' number and the correspondences are not perfect, the strategy, though valid, has a lower success rate in this environment than would be initially expected.
A better strategy is to look at a player's loss rate. The higher the loss rate, the less inclined you should be to ally with that player in the short term and the more inclined you should be to want that player around in the long run. It may seem somewhat contradictory, but makes sense if you want someone you can easily beat in the late game. In practice, this would mean you have a N.A.P. or something similar with a weak player, taking as many of their expansion centers as you can without eliminating them. Simultaneously, you leave them (the weak players) to fight and distract the other better players that you are friendly with but don't directly help while you gain a positional advantage so you can eliminate them. Once the strong players are made insignificant, you eliminate the weak players for the win. (another way to look at it is like vassalage: force weak players to join you to fight the strong players, then then take out the the weak when the strong can't fight back.)
wow... that sounds really mean when i think about it. Good strategy though.