I heard the most likely to develop infections was navel piercings (I heard the figure, and the fact that all the people I know with that kind of piercing had them get infected seemed to support it).
But I can see how this would get infected as well. To heal well, they need to air out and not get in contact with stuff. Breasts being under clothes makes them air out less, and rub against closing more. On top of that they're more likely to get bumped.
The first time I had my ears pierced, they got infected because I thought I needed to move the piercing as often as I could, instead of doing it twice a day and leaving it be the rest of the time. I didn't make that mistake when I got pierced again, and I got no complications. I think I would try to get my nipples pierced when I know I won't have to go out much, so that I can be topless at home more, doing activities that allow me to be sedentary.
When I do go out I can imagine I will want to pad it a bit though, but I'm not sure how bad it is. Infections get the body hotter, and I hear getting it hotter to begin with makes it worse. Not to mention the sweat having nowhere to go if it can't evaporate easily. And since you can't bathe when you've just got a piercing, only shower, I assume prolonged humidity there isn't a good thing.
I'm mostly thinking out loud here. I'm not thinking of having it done right away, in a few months, maybe a year or so, but I like planning and preparing before making big decisions like that.
The fact that it can be removed is actually why I'm drawn to piercings more than tattoos. I like the ephemeral nature of them. I think I would probably get bored with a tattoo that's always the same, while piercings can be changed and removed easily. I might still get a tattoo at some point, because I change my mind a lot, but so far the fact I change my mind a lot has caused me not to get one :P