we had this discussion earlier, and i blamed ubisoft for not giving ED enough time to optimize their game. but it turns out that nvidia is the culprit.
in short, SLI only works in around 16 games right now. getting SLI to work with a game doesn't require developer support, but it does require nvidia to create an "SLI profile" for each specific game. until nvidia gets around to creating these profiles, SLI won't provide any performance benefit whatsoever.
the good news is: nvidia is working on a profile updater, so new official profiles can be automatically downloaded between driver updates. they're also going to release tools for people to create their own profiles, which may be the only way we'll ever see LOMAC support SLI.
so hopefully soon some enterprising LOMAC junkie will be able to make a kick-ass SLI profile for the community.