Sometimes solving the hard problem means jumping into a teamroom in front of a whiteboard and doing some serious brainstorming / design. That is the one thing that is very hard to do effectively over say skype. Often with remote developers this type of problem is solved by a single person without the input of others. Resulting in a less then optimal solution that only one person is knowledgeable in.

As far as really getting into the "zone". What I do is put my headphones on, pipe some white-noise in and in a minute or two it's no different then working by myself in my home office.