[Will88]

Other shoppers wondered why Spam, along with $1.89 cans of Starkist tuna,

Probably because many are stocking up on canned goods such as Spam and tuna, and also canned salmon and chicken. I've bought some extra of all those and I think many others who can't be classified as preppers are doing the same.

[Will88]

I forgot to add. Shop lifters are probably doing a little stocking up, also, so some retailers might find it necessary to put popular stock up items behind lock and key.