Yes. Inviting a strange man to meet you at a bar is not a wise thing to do, no matter how nicely he is packaged. People that do that are taking great risks. imo
It's Natalee's friends' "story" that bothers me...not the introduction.
I don't think it's weird for and 18 year old to introduce herself to a 17 years old.
I'm much more careful about who I talk to now, then when I was younger (especially in high school and college, it wasn't even 'flirting' per se, it was just a hi, I'm so and so.)
I think though that it was mentioned Natalee's best friend's were not on the trip. On the Bill O'Reilly interview a couple of the kids said they hadn't seen Joran before, on a Greta show a couple of different kids said they had seen him. I just don't think there was anything sinister in her acknowledging someone she'd seen around for a few days, with a "Hi, I'm Nat" kinda deal.