I hate it when women say " oh were just friends" not to say that woman can't have male friends but there are some parameter's such as

1. He is ugly/deformed

2. He is gay

*3. He is your brother-in-law/best friends boyfriend or husband

4. She is involved and happy

5. He is a relative (providing they are not kissing cousins)

*- Some woman will indeed fuck their sister's and best friends men.

On the other hand men don't have such stringent policies they are as follows

1. She is a relative (providing they are not kissing cousins)

When men and women are so called friends both straight and attractive here is what ultimately happens she/he looks at the other as a new potential mate wondering why they never thought of this before.  As if this is something new, the person that starts to look at the relationship differently will start to fall quickly and feel that they would be perfect for them that they were meant for each other. This will end your so called friendship.

In closing my view is you can call yourselves friends but someone eventually starts to feel or already feels that there could be more.