Russian visas are not solo traveler friendly. It's the specific dates they require that play havoc with my random travel personality. Grudgingly I submitted a schedule that allowed me 30-days, but only one entry, not the double entry I was going to need. That seemed like a small detail at the time, so not to worry. I headed out with confidence.
A state of mind that would be sorely tested later, but as a committed traveler I don't let idle issues deter me. There's always a solution to every problem. Perhaps not the desired solution, but that's not enough to curtail my movement.
I had the appropriate voucher which is esentially a bogus schedule of travel that one can purchase online. It supported a double-entry visa, but that item was ignored. Side comment on the so-called invitation vouchers; it seems to be a popular motif to require them by some countries, mostly ex-soviet satellites.
However, visas in general can be the bane of the independant traveler. Not only can they dramatically run up the cost of travel, but they can seriously complicate matters. When countries are willing to issue them at the border, it is much simpler. But many countries require travelers to obtain them in advance.
This can be problamatical under a variety of circumstances. Many small poor countries can not maintain Embassies everywhere. So for those of us who stay "on the road" for extended periods, we have to be well-informed as to just where to obtain the necessary visa.
Where you obtain the visa can also determine the price and the type of visa issued. There are good venues and bad venues and traveler beware. The key is to find those venues that offer the best deal--cheapest price, longest stay and most entries. Definately one of the big challenges to the solo traveler.