A lot of little things can add up to some very big things, especially when you harness the power of many. That's the idea behind BigCrumbs, a cash-back service that pays you to refer people to not only eBay but 204 retailers as well, such as Target, Best Buy, Office Depot, Peapod by Giant and GAP. "Earn the highest cash-back rewards at eBay and your favorite stores," trumpets the site's main page, and there seem to be plenty of folks singing its praises.

One user says he earns over $200 a month through his own purchases and just a few referrals he has made. Another, Ray, who has an eBay store selling genuine Coach products, at http://stores.ebay.com/Uncle-Ds-Signature-Cs/ says, "It's a nice little extra for eBay sellers. I just put my affiliate link in every thank you email."

"The site was founded as a way to give people a real shot at sharing in the tremendous economy that they help to build every day," says BigCrumbs founder Vince Martin. "When you look around at MySpace, Google, and even eBay, itself, you find that they all grew primarily by word-of-mouth...friends telling friends, etc. That's been the absolutely amazing power of the 'Net."

And the word-of-mouth does seem to be paying off for the service: "We have a very healthy and ever-growing member community," says Martin. "To provide some context: prior to the recent release of BigCrumbs 2.0, we'd already paid cash back and referral commissions on millions (and millions, etc.) of dollars in purchases at eBay and our other retailers. Since 2.0 (launched Nov 19, 2007), our daily registrations have jumped significantly, and have continued to trend upward."

BigCrumbs is free to join, and to start using it you simply need to login to the BigCrumbs site and use their links to retailers to shop, rather than going directly to eBay or the retailers' page. To make this easier, the site has a "My Favorites" tool you can use to create a list of the places where you shop most frequently. You can also add a "QuickCrumb bookmark" to your browser's bookmarks or toolbar. "Clicking that link activates their credit and takes them to the retailer, which makes it easier to remember," says Martin. "Some members also set BigCrumbs as their home page, which is, of course, a great reminder."

Martin says they'll soon be releasing other optional features aimed at reminding members as well.

You can join as either a "CrumbSaver" or a "CrumbEarner." CrumbSavers are people who are more interested in getting credit for shopping for themselves, rather than attracting referrals, although they also earn when their direct referrals shop.

However, CrumbEarners have a greater potential to earn, as they earn not only when their direct referrals shop, but also when other CrumbEarner referrals of their referrals shop, up to five generations. However, they earn a somewhat lower cash-back reward on their own shopping. In this scenario, as the BigCrumbs site text phrases it, "referrals may grow exponentially across generations."

On the BigCrumbs message boards, CrumbEarners share strategies and celebrate their accomplishments in their growing army of referrals in their downline. Gina, a new member, wrote that she made 15 referrals in just 13 days, and Lisa, who has been a member for about a year, has grown her group of referrals to about 1400. Others, who are not as satisfied with how their network is growing, post questions asking for advice.

Martin highly recommends hanging out on the forums and getting to know other BigCrumbs members: "We have an absolutely awesome group of members who are very savvy, smart, and business-oriented. They are also just plain nice people. They are very helpful, offer great advice, and understand the BigCrumbs concept. In other words, they know that helping each other benefits the entire community."

Beyond those tips, founder Martin advises people to build your profile on the site. "Having an up-to-date profile is one of the best ways to refer others and get connected with the community. Plus, it's just plain fun!"

He also encourages members to get to know the site's referral tools (like the Referral Link Wizard and Referral Email Wizard), and not to engage in high-pressure tactics. "That is definitely not keeping with the spirit of BigCrumbs," he says.

Joining a site like BigCrumbs can pay off - but, as with everything in life, what you get out of it depends on what you put into it. "It really, really depends on how much people use it," says Martin. "We have members who have literally been paid $0.02. On the other end we have some who have been paid thousands."