That wouldn't be a good idea at all. As P3IN said, there are many mischievous people here. NB would become more of a high-school than it already is.
Now "serious" dating is a different issue. Personally, I don't care that much about what image I portray to people. However, if someone here was to seriously (meaning with plans to meet them) consider dating someone...
I'd tell them to make sure they meet the following criteria:
1) I recommend both being in their 20s+ (there's a lot of teens here that loves to gossip)
2) Make sure the person you're dating isn't actively participating in the forum. I know of a few members (men and women) who only log on to read the manga and read the discussions every now and then. There are many members who is as far away from NB as a member can get (without going totally inactive). Unless you yourself is a dishonest person, this minimizes the potential for rumors, and you can be pretty positive they aren't trolling you or setting you up, with the intention to talk about you to their NB friends.
Though I've seen few who have friends while not actually participating in discussions, don't be afraid to look at their convos if they do have a really small amount of friends. Offline, I assume you would observe how anyone treats others around them (let alone a person you're considering to seriously date), or how they talk about others.
3) Make sure you two have the means of meeting each other. Try to be practical as possible about the situation. Obviously, there are several members here who live in the same state or neighboring states, so this probably won't be much of a problem. In this case, it won't be much different from a friend saying, "Hey, I got this girl you may want to talk to.", then you two start talking over the phone, Skype, PC, etc.
4) Assuming you even care what other people think, keep the relationship a secret. There are people who will try to ridicule or belittle the both of you for it. Though most of these people are teens, NB is really not that different, from a high school. You might find a few adults who are more supportive and mature about the situation.
5) I recommend webcamming at some point (assuming you two don't meet first), if you two are very consistent at it, then even parts of their true nature will begin to surface at some point. You can read them through facial expressions, detect change in their behavior, their tone of voice, etc.
Of course there are exceptions to this criteria.
I think I covered the basics. This is just if you two are seriously considering dating each other. Other issues may arise if you two start seriously dating, and I'm obviously speaking from experience. I've conversed with the popular and the unpopular, the loud and the quiet. I've had relationships and I've had breakups. I've been "ridiculed" and "exposed". I've been all around NB, including the dark, scary closets (where all the secrets are).
I totally wouldn't recommend a group though, NB will get very chaotic.