I had a client who came to me, worried that the whole 'user experience' of their software was causing a low conversion rate from evaluation licence to paid license. As it turns out after an in-depth analysis of their product, their concern was well founded.
But here's my point: The only way that the client got on to this idea was because they had a 30 day evaluation license key and they were able to track the trending and relative numbers of downloads or requests for evaluation licenses, and subsequent conversions to fully paid licenses. The conversion rate was unexpectedly low.
Undoubtedly, as Marielle says (and she makes some other great points), the more obstacles in the way, the more users get lost in the process, but unless you can get a handle on the bigger picture of what's happening, it might be a very long time before you pick up on much more important issues, and in the early stages of a product, this could be the difference between success or failure. That's why it is important for the sales guys, but ultimately for everyone involved. This is a good example of when business goals need to override ease-of-use or 'try-ability'.
Of course - it goes without saying that the actual process of getting the evaluation version and/or applying for the license key is an area that needs to be carefully crafted in its own right in order to make it as easy and desirable to complete as possible