Does anyone play two pairs of speakers at the same time?

Not anymore! Your clarity and detail will suffer.

I have a Linn L100 power amp which does accomodate 2 pairs of speakers . I have tried a pair of carlsson OA50's and Sonab 0A14's both upward facing speakers and the soundstage is still apparent . Walls don't matter with these speakers . as someone once said 2 is better than 1 so logic dictates 4 must be better than 2 ? 

I randomly stumbled upon trying this in my existing set up.  I have (2) different amps & (2) different pairs of speakers playing (1) signal from a streamer (via Roon).  It sounds perfectly fine to me.  There’s no ‘heard’ phase issues.  It’s simply (4) speakers playing the source signal at the same time.  Sounds cohesive…I cannot make the distinction of which speakers are playing.  You do have to adjust the volume output via the internal preamp…because both amps are integrated amps in my set up. When I power off one amp there is simply less of everything…but it isn’t bad…the sound just drops down to 2 speakers playing in stereo mode vs quad stereo mode.  If nothing else…fun to try…given I have (2) separate systems in one location that I alternate between.  I have a class A Sugden paired with Spendor 4/5 classics (which are on speaker stands)…& a Hegel H390 paired with Salk Encore towers.  The towers flank the monitors on a wall location with the system of components housed in between.  My outboard DAC has (2) analog outputs…which I send outbound…to each amp.  I don’t think it’s a bad idea (in my realm) per se…just different.  I don’t dare say ‘try this’ using one amp & two pairs of speakers…& of course abandon it if it doesn’t sound cohesive (right) in your rig.  And nope…don’t try it if you think it’s wrong in concept or undesirable in your set up.