[microcolonel]

Well, that will depend on your interpretation of their actions, your local or industry-specific norms, and the actual circumstances of the negotiation.

I have met tough negotiators who uphold their end of the deal just fine.

The people who let me down the most are those who do not even attempt to negotiate on my prices: usually they'll think about it way later, but still won't accept discounts, until they run out of budget. Then you're thinking to yourself “why did they undermine this whole thing by paying me more than they could afford, for something I was willing to negotiate on?”. Then they miss 20k in billing, and you break it off.