One clarification: I wasn’t saying that “most people who use JDate are… the ones who are already synagogue members or belong to groups like Aish,” as you said, but rather the reverse–those who are young, single synagogue members (or involved in Aish) probably use JDate already. The reverse correlation you suggest doesn’t hold; I was on JDate for a few months, and neither I nor any of the women I went out with were regular synagogue-goers–or involved in Aish.

as far as JDate is concerned…i’ll be completely honest, i have never liked the site. all the stories i hear about it are typically negative (except from one of my cousins, who met his wife on the site and my friend’s brother who met his current girlfriend on it).
i appreciate the idea of helping others find their soulmate, but i don’t think JDate should be offered simply as a response to the demographic issue. people don’t need the extra weight on their shoulders when trying to meet potential partners. most people who use JDate are, as Micah said, the ones who are already synagogue members or belong to groups like Aish. they might also be more secular folks (my cousin and my friend’s brother) who would like to meet a Jewish partner but don’t want to do so in a religious setting.

Rabbi Goldblatt brings up a very interesting point. it’s not that people are simply marrying out; it’s that they’re not being shown enough positivity in Judaism. people are more likely to respond to something when it’s presented in a positive manner. if all young people hear about Judaism is that it’s exclusive and old-fashioned, they’re not going to want to be part of it. if they hear it has something to offer everyone whether they are religious or not or whether their partner is Jewish or not, then their attention will be more easily captured.