People do still breastfeed twins - but it is an individual decision. I've never done it but the options are pretty much either a) use the football hold and feed both at once (although maybe that wouldn't work as well until they have the ability to latch on by themselves), or b) one at a time!!
I know personally, if I had twins, I would TOTALLY prefer to breastfeed - or at least try. If they fed as easily as my first daughter, it would still be easier to breastfeed twins than it would be to bother with formula. And if it wasn't too hard, you can always go to formula - but you can't start on formula and change your mind about that!!