This was discussed during The Talking Dead. While it's one way to get the zombies away from the fence, it can also attract other zombies. Additionally, it can attract other humans, which they really aren't too keen on doing.
Anyway, watch Talking Dead, get extra details and clarifications.
No. If your show needs footnotes* to make itself understandable, you're doin' it wrong. Every time it requires reference to some other sow or online resource for the show to understand what's going on, I take that as a knock against the show. When the exterior resource becomes required, I stop watching.
*Technically, they'd be endnotes, I suppose.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.