There needs to be more of boardgame design theory used. By that I mean there are some fundamental ways to design a good boardgame, and a Facebook game has MUCH more in common with a boardgame than it does a computer game or anything else, really.
For example:
1) Come-from-behind mechanisms. If a player feels that there is no way to improve his/her standing compared to those in the lead (let alone actually catch them and rise higher in ranking), then the player is demotivated, rather than motivated.
These mechanisms can be overt or hidden. Overt is an actual feature, hidden is simply that some of the features simply work better if you're lower (or worse if you're higher).
2) Needs Annoyance factor. One of the key components of a good boardgame is the ability of a player to screw with another. This itself is player interaction, which by definition is good and is one of the prime goals of a MMP game (as well as a boardgame). But furthermore it begets additional interaction, as the player in the lead is then motivated to "get back" at the upstart, maybe by invading or something else. Which is further interaction and again more of a good thing. Plus, it sidetracks the player in the lead from pursuing the lead, diverting resources and allowing those in behind more of an opportunity to catch up.
Right now SimWorld has a strong focus on team interactions but very little where one player or one team can sabotage or even simply "mess with" another player or team.
This can also be combined with #1, where a smaller or lower ranked player or team can mess with a higher one, but not vice versa. (Maybe there's simply a cost for the higher ranked, whereas the lower ranked can do it for free; this cost could be scalable by the difference in rank so it could be significant for a player quite a bit higher ranked).
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I could go on, but that's the idea. My suggestion would be for the designers to bring in some boardgame design experts to analyze and offer some suggestions. Back when I worked for a game company we were very much into boardgames and design theory. I've been to the world boardgame championships many times. Would be quite easy (and inexpensive) for SimWorld to bring in someone to offer some suggestions.