Back in the early 90s, I ran several procurements for university computer labs. We were under severe budget constraints, and, as a computer science department, we had constraints not normally found in such labs (for example, we needed to use certain compilers, so they had to support the workstation architectures). We wrote RFPs in accordance with university policies, and, while a number of potential bidders couldn't meet them, the companies in question all understood the constraints, and unsuccessful bidders were constructive, on the grounds of “consider us next time, ok?” All of them were like this, except one. The only time I have ever had someone threaten my job was the Sun Microsystems sales rep, after they lost a competition.