> Even if Google isn't penalising you for that today, they may well tomorrow. So using nofollow seems like quite a rational thing to do for any individual site

> Even if Google isn't penalising you for that today, they may well tomorrow. So using nofollow seems like quite a rational thing to do for any individual site as there isn't any downside as far as I know, only potential benefits. Breaking internet connectivity is a downside for society as a whole.