(FORTUNE Small Business) -- Activists opposed to eBay's (EBAY, Fortune 500) upcoming fee and policy changes are readying for a weeklong site boycott starting on Monday, with buyers and sellers waiting to see if this strike will succeed where past protests have failed.

The boycott, planned to run Feb. 18 - 25, is scheduled to overlap eBay's Feb. 20 rollout of significant changes announced last month.

Sellers say eBay's new policies are likely to cost them more money, but what's really inspired an outpouring of wrath is an adjustment to eBay's feedback system: sellers will no longer be able to leave negative commentary about their buyers. Critics say that will leave sellers vulnerable to negligent bidders and scammers.

"You get bad buyers as often as you get bad sellers," said M. Owens, a Severn, Md.-based seller of high-end dolls that typical go for several hundred dollars each. On such an expensive transaction, having a buyer cause trouble - by, for example, disputing the transaction and requesting a credit-card chargeback after they've already received their merchandise - can be financially devastating, she said.

Owens, who plans to participate in the boycott and avoid buying or selling on eBay next week, is also worried about the impact of a change to eBay's "best match" search algorithm, one of the least-publicized aspects of the upcoming changes. That search method, which will become eBay's default next month, favors sellers with high and detailed customer-satisfaction ratings. Low-volume sellers, like Owens, say this puts them at a disadvantage by burying their listings.

EBay spokesman Usher Lieberman said the company is taking a wait-and-see approach to the boycott talk

"At this point it's still premature for us to speculate," Lieberman said. "We're empathetic with our sellers and understand that they're concerned, and that some of them object to some of the changes we're implementing. On the other hand, we think we have very good reasons for what we're doing."

EBay has no plans for listing-fee discounts or other special promotions next week to combat a potential boycott-related drop in listings, Lieberman said. This week, eBay ran a one-day discounted listing fee special offer on Wednesday, a move that increased listings on the site that day from around 12 million to 16 million.

That special offer was not prompted by the groundswell of seller discontent about the upcoming changes, according to Lieberman.

"We shouldn't be reading anything into that," he said. "We're always testing the price elasticity of our market."

Whether or not the planned boycott will be successful in affecting eBay's bottom line remains to be seen, but auction veterans say this degree of seller backlash to eBay fee hikes and other changes is unprecedented.

"I've been getting about 400 e-mails an hour," said Valerie Lennert, an Anaheim, Calif., doll-clothing merchant who became an unofficial spokeswoman for the boycott after posting a call-to-arms video on Google (GOOG, Fortune 500)'s YouTube.

Past eBay boycott attempts have fizzled, and this one may too, Lennert acknowledged. With millions of individuals selling on eBay, gaining critical mass for any organized action is extremely challenging. But simply getting eBay's attention is a worthy accomplishment, she said.

"There are a lot of people who are really upset, and if we choose to go somewhere else as a group, there won't be an eBay anymore," she said. "We don't think eBay understands that. They think they're invincible, and they don't seem to listen to what we need. Even if listings don't go down, we're reached the main goal: to let them know how upset we are. I'm pretty sure they know that at this point."

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