surely can...

it depends on the personal character of 2 person.. which is the guy n the girl are they matc to be perfect best friend/ good friend or even close friend.

yes TRUST is important.

it happen in me with my buddz which i call him my heng tai. we do call each other darl (darling), or even dear or b**** or ******* or etc.
we could be even more closer then bf/gf... cause we understood each other so well.

n he has become apart of my life like my bro..