I just read these stats on another website:

It is thought that around 12 to 15 per cent of Australian pregnant women carry GBS in their vagina. About one or two per cent of babies born to these carriers will develop GBS disease. The risk of GBS infection is higher among premature babies.

Kinda puts it into perspective I guess.

Also I think that some homebirth midwives use some kind of natural douche before labour or in early labour to kill off any bacteria. YOu could look more into finding out what that's all about if it interrests you