I have mixed feelings about number 7. On the one hand, I do indeed have customers that have read a few web articles that somehow think they know more than me, with nearly a decade of experience with the precise technology they are having trouble with.
On the other hand, I work with vendor support reps that clearly haven't been on the job very long, and whose support skills seem to consist of reading crap off of the knowledge base and trying to push it on me if a few keywords line up. Heck, I have one guy my cases regularly get assigned to that doesn't even go that far.
Example: Customer has a CPU util. display problem on product X running version Y. Dumbass vendor support guy insists it's a dupe of known bug Z. Too bad the bug description talks about mem util. display, on a different set of products, running a different version of the code. He then proceeds to argue with me for ten minutes insisting it's a dupe. He even goes so far as to insist: "The bug never says anything about specific products!" Right in the bug title: "Customers using Products Foo and Bar may experience high displayed memory utilization."! (And my customer isn't using Foo or Bar.)