That's why I do NOT think any harm is being done to this film by Abrams secrecy. The vast majority of the fans who actually care about the secrecy will see it anyway -- secrecy or no secrecy. The rest of the movie-goers (the general population of average movie fans) don't care that much about movie hype 6 months out anyway. They only say to themselves and their friends "what looks like a fun movie that we can see this week".
...And sci-fi/fantasy/superhero films usually look to be the most fun to the average movie-goer (sci-fi fan or not).
Sounds about right to me. I suspect we sometimes overestimate of the importance of the fannish echo chamber. It's a fun way to waste time and chat among ourselves, but I doubt it has much impact on the rest of the world.