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.… Read more