When I was younger, I would have said Hell No but things change over time. If it's a regular thing and happens a lot, it's a problem because of the possibility of STDs and pregnancy. But if it's once in a while, done with someone you can really trust, and with protection then it's not so bad. It's still not for everyone and will ALWAYS carry a risk of infection and baby making (unless you are same sex, of course). I don't think it's ok for teenagers and the inexperienced. I think it can be dangerous for women who don't yet know their sexual personality (i.e., if they are a naturally submissive type that would go along with situations they normally aren't comfortable with if the partner is dominant and confident). It could lead women into situations where they can't fully trust the other person to use protection and treat them with the respect they deserve.
So it's not for everyone and of course, like all sex, it carries risks. So even if you know your sexual personality and shortcomings well, it shouldn't be a matter taken lightly or a frequent occurrence. If you think it's still for you, have fun and BE CAREFUL!