Here's something you may not be aware of: You and I have a contract. "Huh?" you say? "I didn't sign nothing!"

Whenever two parties exchange value for value there is a contract, whether it's written, oral or implied. Little kids make contracts. "I'll trade you this delicious tofu sandwich for your Twinkies." You sign a contract with the phone company, and in exchange for a monthly check, you get to listen to Mom complain about your sister. You engage in implied contracts every day. When you exchange cash for gas, it is implied that you will receive gasoline rather than Gatorade. If you want to see a really complicated contract, sell a book. My publishing contracts run about thirty pages and cover everything from schedules to spelling out rights and royalties to how my name will appear on the cover. Nothing is implied or inferred. If it isn't in the contract, it doesn't exist.

Oral and implied contracts are binding, too. For instance, I have an implied contract with steve-o-meter. This site provides the venue where I can post my essays, and further my mission to make eBay a safer, more civilized place to do business. In exchange, I write about topics that draw readers, which means more traffic to the site for steve-o-meter. It's implied that steve-o-meter will respect my copyright and will refrain from tampering with my writing. It's implied that I will use the blog space responsibly by not spamming or publishing porn.

Breaching contracts can have serious consequences. Little kids understand that. How many times have you said, or heard, "No give-backs!" In grown-up world, breaching a contract can land you court or ruin your reputation, or both. When you register on eBay you have to agree to the terms and conditions in order to buy and sell. Failure to comply with the terms can get you banished from eBay. If eBay breaches its terms, they lose users and revenue. Terms can be changed, but only if both parties agree. There's a lot of howling over on the eBay blogs about recent changes in eBay's terms. Here's the thing. It's eBay's site, and they set the terms. Ebay is not required to negotiate with users to change their terms. Negotiation is in the form of use or don't use. If the new terms are unreasonable then eBay will lose more users than it can afford to lose. It's an exchange of value for value, and if either party feels the value they receive isn't equitable to the value they give they can walk away.

Some contracts are unenforceable. If I hire a hitman to whack the old man, the assassin can't take me to court because I don't feel like paying him. No court will sanction any contract that involves illegal activity. That applies to eBay, too. If you sell counterfeit goods or stolen goods, you're involved in illegal activity and no court will enforce the contract. Ebay won't sanction the sale either. Any contract where one party receives value, but the other doesn't isn't enforceable. On Judge Judy there was a case where a guy bought something expensive and in return got a picture of the item. The seller thought she was covered because she promised to deliver what was pictured. That wasn't a meeting of the minds. Technically the seller hadn't done anything illegal, but she had breached the contract because there was no exchange of value for value. Judge Judy slammed that seller, but good.

Buyers and sellers have to be certain that any contract they enter complies with eBay terms and policies. If a seller overcharges for shipping and handling, for instance, and the buyer pays it, then both are guilty of circumventing fees. My suggestion for buyers is if something seems off, read the policy regarding the worrisome term. EBay's policies and terms override any terms the seller might set forth.

Changing terms when the other party is not in a position to agree or disagree is also a breach of contract. For instance, a buyer contracts to buy, and then informs the seller that they won't be able to send payment for three weeks. Or the buyer wins an auction then discovers added fees that weren't properly disclosed in the listing. The injured party has the right to open a dispute and cancel the contract.

EBay does enforce its terms and does mediate disputes, but just like going to court it can be a drawn-out, frustrating experience. Smart eBayers understand the terms, written or implied, before buying or selling.

By the way, regarding our contract. If you've read this far, then you've given me a few minutes of your valuable time, and I've given you some information and food for thought. Our contract is fulfilled.