[CleighMoores]

I think less of a 'viable strategy' and more they have more utility now with more units that can drop or harass worker lines easier. I've certainly found cannons - particularly in mid to late game - are super helpful at deterring drops, and one cannon to scare off Oracles, or to detect mines/DTs either in mineral lines or at choke points feels much more natural now.

ie. Newkirk bottom left spawn I put 3 cannons down to the right of my main to deter drops and it worked a charm without having to move units back and forth.

So I think early game it's still pretty standard compared to WoL, but they seem a necessity for most aggressive matchups otherwise, even if it's just a couple. Saying that, all of that can be negated with proper map vision with Obs or successful scouting xD