There are boyfriends, then there are lovers, some we call partners, husbands, better halves so on and so forth.
I believe that a lover turned husband is very different from best friend turned husband. You don't create sparks they happen if they have to. With the best friend the jars for trust, understanding are already full when the relationship changes to legally wedded partners. You already know so much about the other. A lover on the other hand may or may not become a best friend. Its good if he does but then again its fine if he doesn't. Everybody doesn't fit into all costumes. That's why married folks still have friends that they continue to confide into with out the fear that it may hurt the relationship or the fear of being judged. I think it may in fact be very healthy to have friendships that are outside the marriage. Sometimes our friends may give us a perspective which we accept wholeheartedly while we may have rejected it had our partner said the same. Its like .. after a while we don't listen to our mothers while they are trying to drive good sense into us... leading to "I told you so".
I may be romantic with my lover but not my best friend and what happens when its the same person. Well in that case, there is a newness to the relationship and I will look at that person in new light and he will find me different too. Our expectations from the same person will change and then one may realise that someone is a great friend but not a great partner. Then you end up losing the friend and not getting the partner you wanted. I believe that our fears are different in each relationship we value.
Somehow I feel that friends should be friends and lovers should be lovers and mixing the two should be avoided. Keep life simple ...silly!