I wouldn't say I have brand loyalty the same way that Macro drinkers seem to, but I definitely have some brands that I am quite fond of and do feel some loyalty to. They are mostly the local New England breweries I grew up on (Otter Creek, Smuttynose and Ipswich in particular). I'm not guaranteed to like every beer they brew, but they are definitely how I developed my taste for beer. If given a choice I will typically reach for one of their beers first.
For example, I judge every Oatmeal Stout against Ipswich's by default because that's what introduced me to the style and it's still my old standby to this day. Another example, Otter Creek's beers have this minerally/steely character that a lot of people don't enjoy. I'm the exact opposite - this is one of my white whales in homebrewing. I love this flavor in a lot of styles, but I just haven't been able to nail it down yet.