I'm a John/Rodney shipper and 99% of my flist are J/R as well. I didn't even really think about John/Carson at all (but maybe that's because I love Carson, but see him as a completely nonthreatening, nonsexual being.) I don't see much JOhn/Teyla, but then I often hear about them, they sort of exist peripherally and seem to have a bigger impact on fandom? People reference them more often?
Or maybe I'm just talking nonsense.