Are you talking about the Arcane Wonders Forum community? Or specifically the Mage Wars Community? Or the Mage Wars Arena community? Mage Wars overall has 4624 likes on Facebook, which is a lot more than Arcane Wonders has (1395 likes). Arena and Academy do not have separate facebook pages.
Take this with a grain of salt since I haven't actually read the study yet, but wikipedia cited a 2014 study published in the Journal of Medical Internet Research which "found that the 1% rule was consistent across four separate digital health social networks (support groups for problem drinking, depression, panic disorder, and smoking cessation). During the study period 63,990 users created 578,349 posts, but less than 25% of users made one or more posts. The applicability of the 1% rule was confirmed as Lurkers (90% of users), Contributors (9% of users), and Superusers (the 1%) accounted for a weighted average of 1.3% (n = 4668), 24.0% (n = 88,732), and 74.7% (n = 276,034) of all content.[6]"
So we have 4208 users on these forums, and over 4624 likes on facebook. On the Mage Wars forums you can read stuff that people post without an account, but in order to read facebook posts you have to have a facebook account. This makes sense with what wtcannonjr said:
BoardGameGeek has Arena listed with 1115 Fans and 8542 owners.
If over 4000 people like mage wars on facebook, and over 4000 are members of these forums, and over 8000 people own the game on boardgamegeek, then chances are that either those two 4000's are approximately the same population, in which case the remaining ~4000 BGG users are not or no longer mage wars fans and haven't updated their ownership status, or one of those two 4000+ populations includes more of the active members of our community and the other includes the less active members. This depends on what percentage of facebook users are lurkers there, what percentage of those lurkers actually click the like button for most or everything they like, how many facebook users update their liking status for things they no longer like and how frequently they do so, and how many users on boardgamegeek buy games that they end up not liking and not updating their owner status when they get rid of their copy of the game.
In light of the BGG statistic, I would suspect that there are actually a LOT more mage wars players in the world than we realize (since the majority of people who play mage wars probably don't have a BGG account) It still really depends on how many people play the game only casually or in real life who do not participate in the forums or who have BGG accounts but not facebook. I find it unlikely that ~50% of BGG users who buy the game end up not liking it. Therefore the actual number is probably significantly higher than facebook likes, bgg ownership or forum membership individually. Maybe if you add all three together that would be fairly close to the number of mage wars fans that exist and then subtract overlap.
So if there were no overlap between AW forum membership, MW facebook likes and MW ownership on BGG, and if there were no out of date MW facebook likes nor out of date MW ownership status on BGG, then we would have at least 17374 mage wars fans total.
https://en.wikipedia.org/wiki/1%25_rule_(Internet_culture)