Don't bother with the tablets. Just clean your camelback (or wing) with some white vinegar and rinse it thoroughly. I use a gun barrel cleaning rod to clean the hoses on my camelbacks. Works like a charm and gets rid of any of those nasty molds that definitely do grow in these types of bladders with or without sun.
As for the original post, the molds definitely smell bad (assuming that it's mold and not just stinking stale water), but I've never seen or heard of any data that suggests you're more likely to get sick from breathing around them. That said, mold isn't something you really want in your lungs so clean the wing regularly.
To whomever said there's no oxygen for things to grow, you are aware that water contains oxygen, right? Not to mention every time you dive with the thing there is air in there from inflating it.
