I recently read a blog post headlined roughly Why you should never rent a mailing list. (I'm purposely paraphrasing here; I'm also not going to link to it because that wouldn't be nice. If you want to find this particular blog and its post, you're going to have to do some digging.)
The content of the post was a list of mishaps and horrors that could (and apparently did) happen when amateurs get in over their heads on the list rental market. Things like being overcharged and getting insufficient response.
But those things don't happen to experienced professionals. Being savvy and successful at renting lists protects you from the typical disasters. Like most things in life, going in half-cocked and unprepared usually means you'll have a bad experience.
So what you get from reading that blog post is an admission of inexperience -- positioned as useful knowledge. "Don't rent mailing lists" is incredibly bad advice for most organizations. These guys sent in the Cub Scouts when they should have sent the Marines. And they were too inexperienced even to know that they created their own problem.
Not everyone who reads the blog will know that. Like most blogs, it positions itself as an authority, a thought leader, a resource for nonprofit organizations. And with a combination of good-looking design and an authoritative voice, it seems the part.
There's no quality control on the internet. Anyone can say anything, and there may be little to warn you that they are clueless. One hint is this: When they make a blanket statement that you should not do something that thousands of organizations do successfully all the time, you might want to take the advice with a grain of salt.
So caveat lector -- reader beware. Just because it's on the internet doesn't mean it's good advice.