I don't think many people realise the responsibility they are taking when they sign the back of a check.
When someone writes you a check and you sign the back of it (endorse it) to deposit or cash it, you are basically telling the bank that YOU will make good on this check. If the check is drawn on another institution it is impossible for them to know right away if there are funds in that account. They will not know for a couple of days. This is why you have to have at least that same amount in your account if you are cashing it (say it is a check for $100, you have to have at least $100 in your account). This is for recourse. So if the check gets sent back to your bank then they will take that money out of your account AND you will get charged a fee for the check being sent back.
I certainly never knew what I was agreeing to by endorsing a check. Here's a little hint: if you bank at, say, Chase, and someone writes you a check drawn from a Chase account, you will know immediately whether that check is good or not.