Totally agree. Nearly all of my male friends have seen each other naked briefly (changing in hotel rooms, etc.) or at least seen each others' dicks (pissing outside, etc.). I've spent more extensive time naked with a subset of friends, in situations like open gym showers, open shower, nude beaches/skinny dipping, nude hot tub, or with roommates who shared my level of comfort with nudity in the apt.
I definitely feel a special bond that comes with prolonged and/or frequent nudity. Part of knowing someone is knowing what they look like...face, hair, eyes, height, build, etc. With the subset of friends with whom I've shared nude experiences, we also know what each others' dicks look like. In that sense, we know more of each other.
I also think there is a bond that comes with learning that we have a shared value that it is normal and healthy for men to feel comfortable naked in front of each other.
With gay friends, there is an additional factor that there we have a shared appreciation for the male body, so even in completely non-sexual situations, we can enjoy the sexiness of seeing and being seen naked.
An additional factor with straight friends with whom I've spent naked time, is that they know that while I am attracted to the male body, they also know that I would never do anything to make them feel uncomfortable. The fact that they seem completely comfortable being naked in front of me and seeing my naked body indicates a powerful sense of trust.
So yeah...nudity promotes bonding for me!