This isn't that different from the thread on
weeniecello. To me, there's something a little amusing but not all that interesting about the typical "duuuuude! have some relish-flavored vermouth with that hotdog-flavored vodka" scenarios. It's nothing that I'd really want to drink other than as a temporary amusement.
But fat-washing is a powerful and compelling technique that is far more interesting than mere novelty infusions. Just about every taste and aromatic compound that is soluble in fat is also soluble in alcohol. All that is needed is to mix the fat with the alcohol, wait a while, freeze the alcohol and skim out the congealed fat. Substantial taste and aromatic compounds will have transferred from the fat to the alcohol. Right now, Eben Freeman at Tailor and our own donbert at PDT are doing the most interesting things with fat-washing of which I am aware.
A good example of this would be PDT's
Benton's Old Fashioned, which is built on a foundation of bourbon infused with fat from rendered Benton's bacon. It's not a punch-in-the-mouth of bacon right up front, but, especially after the first few sips, rather a subtle hint of smokey pork in the finish. This is a unique, interesting and delicious cocktail that is much more than a novelty.
Part of the trick, of course, is picking the right spirit into which the fat will be infused. Vodka is not particularly interesting, in my opinion, and will typically yield a product that doesn't have much potential for serious mixology.
Perhaps at some point we can start a serious thread about fat-washing. It's a technique that is only just beginning to be explored by mixologists. I'd like to learn more about it, and I'd also like to popularize the technique (which is not difficult to execute).