The majority of fine scotch distillers sell casks of their product as a whole for blending purposes as well as to private buyers. Usually the distiller name will be placed on a blended product however not the logo. This is an indication that the product is indeed blended and not single malt.
Most independent bottling companies will bottle products from single casks and may or may not be from the original bottling source. At this time many renowned distillers are trying to end the open market of bottling operations as it is infringing on their overall sales.
Some malt companies will incorporate more than one batch of their scotch into the cask selling to ensure the independent bottlers from selling it as a single malt product. Many independent bottlers will use merely a geographical region or an alias of the distiller, as to avoid any legal repercussions. This method of legal sneakiness is known as "bastard bottling". Either way the society of scotch malt whiskey can still track the product by the distiller number.