I think it really depends on the rabbit.
Many rabbits can get by absolutely fine without another rabbit partner, as long as they get lots of attention and socialising time with their owner. Some rabbits don't WANT a partner.
However, rabbits are social animals, and lots prefer to be in the company of another rabbit, so I think that when you get a rabbit, you need to keep in mind that one day you might realise that your bun would be happier with a friend.
I think start off with one, or, if you want two and have the space etc. already, then why not get an already bonded pair from a shelter? At least that way you know there won't be any bonding problems, and the possiblity of them not getting along.
I believe that indoor bunnies are much less likely to need a partner, as even when they are in their pens, they are still in the company of others. And even when you're busy, they are always still around you, every second of the day
Just my :twocents
Jen