The wall acts to reinforce the sound, particularly bass energy. When a speaker is designed to be placed near the corner, the designer takes this into consideration when balancing the sound. Of course there are tradeoffs to corner or near back-wall placement -- the soundstage does not seem to float in space and have the same sense of front-to-back depth. Some corner placement speakers, like horn designs, have a relatively narrow dispersion pattern to minimize interference, at higher frequencies, with the side wall.
Naim speakers are quite good placed close to a wall. They are balanced for that. One of the best brands for such placement, in my opinion, are Audionote speakers. Another speaker that impressed me very much while being placed close to the back wall is the Gradient Revolution.