This leads to two things, in practice:
1. People can have two best friends: a "beste vriend" and a "beste vriendin". As opposed to simply one non-gender-specific "best friend".
2. When introducing people, the word "friend" is ambiguous. For example: "this is my friend Mike" ("dit is mijn vriend Mike") can mean friend, or boyfriend. The more neutral "a friend of mine" ("een vriend van me") is often used instead. So, unless the relationship is already clear (or the person's sexuality is known), the possessive is avoided. Also, the comma seems to be important: "This is my friend Mike" implies friendship in Dutch, but "This is my friend, Mike" can imply a more intimate relationship. Of course, telling casual stories like "My friend Mike and I were at this bar the other night..." becomes essentially impossible; it's unclear whether this Mike is a friend or a boyfriend.
A dramatic tearful "But I thought you were my friend" is, of course, out of the question.
Is there any similar situation in your language, or in languages you know?
[x-posted to linguafags]