1: Costco rival ShakeUp changes member perk policy.

2: Long-standing perk alteration could sour customer loyalty.

3: Risk of backlash in response to popular benefit adjustment.

4: ShakeUp's decision may result in negative customer impact.

5: Potential drawbacks to key perk modification by competitor chains.

6: Customer dissatisfaction looms following ShakeUp's perk change.

7: Impact of altered perk on ShakeUp's competitive edge.

8: Rivalry heats up as ShakeUp risks customer loyalty with perk shift.

9: Consumer response uncertain following ShakeUp's controversial policy change.