Is it ok to stack LPs horizontally?

In addition to warping (which I never considered) I always thought that the extra weight of storing horizontally would cause dust and dirt to be pressed into the grooves. So I always store vertically. 

@heretobuy      Goodness, that rig looks highly unstable on its tiny angled feet.  Anyone who has lifted that number of LPs knows how heavy they are.

A dog or a small child could accidentally knock it over and the falling LPs cause injury or worse.  I wouldn't have it in my house.

Horizontal storage will cause excessive ring wear at bottom of pile.

Not just a warping issue but any dust or crap on an LPs surface with be further smashed into the groove. No no no.

overall, I would say its not a good idea.
Records are not an even thickness, the label area stands proud and so does the outer edge, it has a thickening or bead designed to guide the stylus into the start groove, it also helps in the manufacturing process.
While stood "almost" vertical is not ideal, I think its better than the combined weight of many pressing down on those at the bottom of the horizontal pile.
Though you could argue, that in the thick sleeve, this can be accommodated.
I think they are stored vertically, purely for ease of use. If you have a horizontal stack, its difficult to pull one from near the bottom and worse trying to return it to the same location.