Grammar Brigade: Semicolons, the forgotten punctuation

I was going to do a lesson on using semicolons.  However, I cannot possibly outdo The Oatmeal's semicolon lesson.

I can, however, paraphrase it for those too lazy to follow the link, or those who fear being sucked into The Oatmeal's endless supply of ridiculously funny pages.  (Go ahead and bookmark the page for later.  You know you want to.)

Semicolons are usually used to connect two independent clauses together.
ex:  I love morning glories; my mother loves hydrangea.
This should only be done when the two independent clauses are actually related.
NO!: I love morning glories; Sister Anne drove the van to a conference in Italy. :NO!

They can also be used in sentences wherein there are already commas (for the purposes of clarity.)
ex:  I have visted Austin, Texas; Memphis, Tennessee; Juneau, Alaska; and New York, New York.
ex:  My teacher, Mr. Norris, loved apples; and when finished eating, he would bury the cores under piles of nasty, steamy tar.

Questions, besides why Mr. Norris loves to bury apple cores beneath tar?