If you've been in business for a while then you've probably learnt all this already. If you haven't you might end up learning it the hard way.
A lot of business relationships are built on "trust". In many respects the concept of "trust" is quite intangible. But it's one of those things that you come to rely on instinctively. So when a vendor (or customer) has built up a degree of "trust" with you (or vice-versa) you're able to conduct business. Without a certain degree of it you probably wouldn't be able to operate.
Unfortunately, at times, the harsh reality is that "trust" is simply not enough.
A person's "word" is not good enough.
You need to get everything in writing and be sure that you can take action should they fail to meet their commitments to you.
A simple handshake or verbal agreement just simply won't cut it at times.
It's unfortunate. But it's reality.
Over the past 10 years or so that I've been in business I've been let down several times, but only once or twice has someone blatantly lied to my face.
It happened again recently and it was nasty. I'm not sure what the outcome of the latest "issue" we've run into will be exactly, but there is a lesson to be learnt.
Simple trust is not always enough.
I'm not sure what *is* enough. A contract can help, though even those can be ignored by companies that are facing bankruptcy, which in the current economy is a real risk.