I have a terrible sibilance problem with my own voice. And I think the few condenser mics I own exaggerate this. With my recordings, there's definitely a proximity effect (worse if I'm too close, even at low recording volumes). It occurs at different frequencies, i.e., ~ 5200 Hz for 's' and 't' consonants, and ~ 4000 Hz for words starting in ch (like 'church'). It's much more pronounced when I'm singing more forcefully, e.g., during parts of a song with higher emotion. I do believe there is a big difference in sibilance between individuals, as I've had other people record vocals through my system with minimal sibilance. I've slowly trained myself to enunciate a little differently on the sibilant consonants, and that's helped a lot. I will also punch in or re-sing certain parts as many times as necessary to minimize the sibilance. I may be a bit sensitized to this, as Ash suggested, but it's a real problem, and all my efforts to minimize sibilance pay off in terms of a much more professional sounding vocal take. Despite my techniques to minimize it at the source (during recording), I still usually have to apply a de-esser, and I've found that the one from Waves is the best. It has a very quick attack and release, and so it only minimally blurs the consonants, as long as the threshold slider is not pushed too far. I can actually use the shelving filter option (as opposed to a parametric band) set at ~ 4000 Hz to quash a major percentage of the sibilance without taking the edge off the high end of the vocal, although sometimes I will add a high shelving boost to the EQ plugin to compensate. When I'm dealing with more substantial sibilance on an otherwise good vocal take, I may use two de-essers, usually placed relative early and late in the vocal plug-in chain. The before-after comparison is quite impressive. It's interesting to note that the second de-esser is still catching some sibilant pops that slipped by the first one. On top of all this, I may use precisely placed volume automation to take the edge of some words, if I'm too lazy to re-record.
