Computer dunce here. I have a language student staying here who spends around 6-7 hours a day on Skype. I do have a fairly generous download limit on my broadband package which I've never worried about as I couldn't even get close to hitting its limit, but I'm wondering whether someone being on Skype for that long every day for a month might have an impact that I'll notice.
Don't get me started on how irritating it is to have someone shouting their heads off in Portuguese for hours and hours every day...