There are limits. For instance, i dont think its right for a man to accompany a married woman to her house when her husband is not around (and vice versa). Sometimes too often, people cheat on each other and with who? the best friend! So there should be limits. I also don't see the reason for a single man to be calling his best friend's wife to just 'chat' it up. Its fine in a group setting. Thats just my two cents:)