I just had this conversation with one of the yudansha in my dojo. Pretty much the sentiment is that there is nothing wrong with meeting someone in the dojo, just keep the dating and affection of the mat. We have quite a few couples in our dojo and even our head instructors are husband and wife so prohibiting dating anyone in the dojo would be a bit silly.
Sure there are women out there who join to meet a guy, but I think more women just join to meet new friends. But there are men out there who join to meet woman. Either way if one party is too aggressive in their flirting then you're apt to drive them away. Although, the person that gets driven away usually is the newbie. I've seen it happen. A new good-looking woman joins and then four or five guys are asking her out -- on the first night she was in the dojo. One guy asking her out would have been harmless but four or five was over the top. Needless to say, she didn't come back. And to top it off, I think she was married. They didn't even bother to get to know her, and they all came across as pretty need, which turns some women off. It's hard enought to keep newbies around, they last thing we need is a bunch of guys flirting with a day one newbie. That'll send a lot of people running for the hills.
If they really wanted to date her, let her settle in the dojo first, let her get to know you and you get to know her. Then wait to see if there could be anything. Go out with a group from the dojo first, then ask her out. Not pounce on her (or him) like fresh meat.