How far do people go to save 2 cents/litre on gas?
It depends how bad at math they are.
That said, a lot of retail businesses do face serious competition from online outlets.
SirJohn's article was specific to restaurant costs, and I assure you that the Tim Horton's drive-through has nothing to fear from Amazon.
Higher prices in the local stores due to minimum wages will push a lot more sales to online outlets and hasten the end of the local shopping option. Some may see this as a good thing but it does mean fewer jobs for the people that are supposedly helped by higher minimum wages.
Brick-and-mortar retailers have been under pressure for many years. Each time Wal-Mart opens a mega-store in an area, lots of smaller retailers disappear. It's not like this is a new trend. North America has lots of abandoned shopping malls, and that started happening before online shopping became a big factor. The arrival of Amazon and so-on signal new worries for retailers, but I have a hunch that the ones who've survived Wal-Mart will survive Amazon as well.
There are some goods that are ideal for online purposes. For others, not so much. You can't tell how comfortable a shoe is by looking at a picture.
Change is the only constant. When the motor-car arrived we didn't say "we have to stop this or all these blacksmiths will be out of work!"
-k