There are arguments abound on the web about this and in many ways I might agree about ruining a fine brew with a shot of liquor in it. A quick scan on the Wikipedia entry on the subject lists a range of so called “beer cocktails” that seem to be a bunch of pints with a shot of something in it, often still in the shot glass! That is not a cocktail – that is a bunch a frat boys getting drunk by spiking their beers and calling something offensive like “an Irish car bomb” or vaguely militaristic like a “depth charge” or “U-Boat”.
Classic cocktail ingredients have relied on good quality ingredients for many years (not always, though – some early cocktails or punches mixed in things that would soften the harsh taste of badly made spirits). Whiskies, rums and gin make the basis for many cocktails, and their flavour is paramount; the better the spirit, the better the cocktail can be. It is the same with beer, in my opinion, and those great flavours that can be enjoyed on their own, can form part of the picture to make a great tasting beer cocktail.
The secret to any cocktail is getting the balance of flavours right. Sweetness, sourness, acidity, bitterness, body and alcohol need to have a certain synergy that culminates in the flavour that the creator is trying to achieve and beer can add a new dimension to the list of more common ingredients. The problem with merely adding a shot to a pint is that the beer drowns out the flavour and rarely offers anything other that making the beer stronger and often sweeter. The beer needs to be in smaller amounts to allow the other ingredients a chance to offer some complexity and nuances, as well as making a drink that resembles a more traditional cocktail (long or short) and more interesting to drink!
I am starting to compile some beer cocktail recipes here that have merit and have been sold at a bar or restaurant so please help and submit some recipes with their creator, year of invention and where it was first sold (if possible). Cheers!