Another clothes-maker, noticing the popularity of your design and the growing frustration of your customers (and potential customers), creates clothes that look and feel exactly like yours, and make them available with free shipping online within a few hours of you making new designs.
Your customers (and potential customers) who don't live in Santa Monica, or those who can't make it to your store during business hours, or those who take public transit—frustrated with the roadblocks you've put between your clothes are their wallets—start buying from the pop-up e-tailer.
You complain about how this (and this alone) undermines your business. Your customers say you forced them into it. Neither of you is right.