I'd say two people pirating a movie is exactly double as illegal compared to one person doing it. At least in total. And sharing a legal copy with friends is completely fine in lots of jurisdictions. I mean other terms and conditions apply... You might have to circumvent some copy protection to be able to do that, and that might be a different offense. But apart from that, it's similar to lending them a DVD (Well, actually since you're copying it, it'd be more like burning them a copy of one of your DVDs).