With all that technology, shouldn't Amazon have an effective way of authenticating sellers, recognizing bots and fake IP addresses and blocking banned images, even if ultimately the fraudsters make up a tiny percentage of merchants?
"If they're giving me such a runaround and not wanting to take down stuff, I'd think on the flip side there would be just as much oversight and rigor for someone to become a seller," said Nidhi Chanani, owner of Everyday Love Art in San Francisco.
Chanani said she recently removed all of her illustrations from Zazzle, because the exact same mugs, pillows and phone cases were too frequently finding their way to Amazon. She's now focused on building an audience for her own website.
Read MoreNetflix vs. Amazon
"I can't afford for somebody to steal my stuff and be selling it," she said.
Zazzle is well-aware of what's happening. The Silicon Valley company, which is about 1/400th the size of Amazon, has improved its watermark on high-resolution images, making it virtually impossible for counterfeiters to take them. But the bad guys still have access to the lower-quality images on the website.
On Tuesday, Zazzle posted a form for designers to fill out with links to unauthorized listings on Amazon and data on products that have been removed only to reappear later.
Zazzle has its own business to consider. After all, plenty of consumers would prefer the discounted items on Amazon over the higher-priced originals on Zazzle.