ZDNet has a great article on the "Top 10 Reasons to Avoid IT Salespeople." But really it's a treatise on how to avoid them. The article doesn't mention the easiest way to turn the tables on proprietary salespeople: buy open source.
Open source gives customers real information about a vendor's technology - what it can actually do, and not what some salesperson is hoping it will do:
Mindless optimism - The biggest complaint that Dorian Spackman has about IT salespeople is the constant hyperbole about products, prices and performance. As IT director of Group Up, a media-distribution firm, Spackman regularly meets with new suppliers working with internet technologies - and is heartily sick of trying to work out what he can and can't believe.
"They tell you the next iteration will hit the market in six months; that this thing will offer massive improvements and will change your life," Spackman says. "But what I hear is that they hope it doesn't slip too badly, and it's better because it's more expensive, not because it actually offers any more features. And, yes, it might change your life, but probably because your staff will spend most of their time on the phone to a product-support service in Bangalore, reading out the licence number for the 33rd time."
Open source also gives a customer leverage over its incumbent, proprietary vendors by providing a real alternative to proprietary bloatware. And since code can't lie, even if the salesperson might try to do so, a buyer is in a better position to make an informed choice with open source than with proprietary software.