I'm pretty sure that a "blended malt" will be a blend of any number of single malt whiskies, whereas a normal blended whisky is made up of (usually) inferior grain whisky mixed with some malt.
I'm sure you can get some excellent blended malts (also some good blended Scotch), but I would be way more inclined to buy normal single malts. This way you know exactly what you're buying, where it comes from, how it's made etc, and it's also interesting to find out about the distillery, whereas with a blended malt you don't know any of this.
Edit: Pulled from Wikipedia regarding the definition of blended malt:
Quote:
Blended malt whisky—formerly called vatted malt or pure malt (terms that are now prohibited in the SWR 2009)—is one of the less common types of Scotch: a blend of single malts from more than one distillery (possibly with differing ages). Blended malts contain only malt whiskies—no grain whiskies—and are usually distinguished from other types of whisky by the absence of the word ‘single’ before ‘malt’ on the bottle, and the absence of a distillery name. To qualify as a Blended Malt, the mixed single malt whiskies are matured in the barrel for 1 year,[citation needed] after which the age of the vat is that of the youngest of the original ingredients. A blended malt marked “8 years old” may include older whiskies, with the youngest constituent being eight years old before vatting.[citation needed] Johnnie Walker Green is an example of a blended malt. As of November 2009, no Scotch whisky could be labeled as a vatted malt or pure malt, with Scotch Whisky Regulations requiring them to be labeled blended malt instead.[3]