Can alcohol bottles (especially liquor) be stored on their side?
Beer bottles should be stored upright.  This is to minimize contact (and hence oxidization) between the beer and bottle cap, and (for unfiltered beers) to keep any sludge on the bottom of the bottles.  (How To Store Beer)

Wine should be stored (mostly) on its side.  This keeps the cork moist; and a dry cork can shrink and allow too much air into the wine bottle.  (Storage of wine)  But note that:


  Champagne and other sparkling wines tend to age better if they are kept upright.


The rules for liquor aren't as defined, but it should generally be stored upright.  (Taming Your Liquor Cabinet).  It's stored that way at the factory, and it's shipped and displayed that way.  Also for many "fancy" bottle types, the bottle won't even sit properly on its side.  Also, alcohol in liquor can leak through - or even break down - whatever material is used for the cap.  But it's generally safe to store liquor bottles horizontally in the freezer for a time.  It depends a lot on the specific bottle and cap in use.