I think that Sunnydale can largely thank Anya for not having a lot more incidents of chaotic inexperienced magic users (e.g. the Trio) causing mayhem. Why? Well, when Giles sold Glory 2 items that could be used for a dangerous spell, she called him out, basically asking why he would sell anyone such a dangerous combo. This indicates that Anya is at least generally aware of what shouldn't be sold to customers or what to watch out for, and implies she wouldn't have sold Glory the items. Furthermore, when the gang is under the Tabula Rasa spell, we saw that an amnesiac version of Anya was able to perform potentially dangerous spells using only a single spell book, including conjuring rabbits and a sentient skeleton (that Giles sword fights with). This indicates it would be entirely possible for people with no idea what they're doing to perform irresponsible magic fairly easily.
Basically, Anya prevented a large amount of even more crazy whacky things from happening in Sunnydale
We needed scenes of Anya calling Buffy and saying "Someone just bought these dangerous items and he was clearly a vampire intent on ending the world, you should go stake them"
Buffy "Why did you make the sale if you knew this could end the world??"
Anya "I jacked up the price and got him to pay triple. I mean, he thought he was about to end the world so he wasn't going to care if I took all his money. Now go kill him before he does the spell, this is your sacred calling"