What is vulgar?

"It is low hearts and not low brows that are vulgar."

~C.S. Lewis, Selected Literary Essays, "High and Low Brows" (1939), para. 18, p. 275.

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From the American Heritage Online Dictionary:

VULGAR:
1. Crudely indecent.
2 a. Deficient in taste, delicacy, or refinement.
b. Marked by a lack of good breeding; boorish.
c. Offensively excessive in self-display or expenditure; ostentatious: the huge vulgar houses and cars of the newly rich.
3. Spoken by or expressed in language spoken by the common people; vernacular: the technical and vulgar names for an animal species.
4. Of or associated with the great masses of people; common.

Word history:
The word vulgar now brings to mind off-color jokes and offensive epithets, but it once had more neutral meanings. Vulgar is an example of pejoration, the process by which a word develops negative meanings over time. The ancestor of vulgar, the Latin word vulgaris (from vulgus,Vulgaris also meant “ordinary,” “common (of vocabulary, for example),” and “shared by all.” An extension of this meaning was “sexually promiscuous,” a sense that could have led to the English sense of “indecent.” Our word, first recorded in a work composed in 1391, entered English during the Middle English period, and in Middle English and later English we find not only the senses of the Latin word mentioned above but also related senses. What is common may be seen as debased, and in the 17th century we begin to find instances of vulgar that make explicit what had been implicit. Vulgar then came to mean “deficient in taste, delicacy, or refinement.” From such uses vulgar has continued to go downhill, and at present “crudely indecent” is among the commonest senses of the word.
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So what do YOU think Lewis means here? How do you feel about vulgarity?

I've been thinking about this a bit lately, as the new message boards for TornadoBooks.net are up and running and sexual subjects and profanity are allowed on those message boards. Oh the glee some people find in this verbal freedom! ;-) Also, I read an article the other day, titled "How to have a successful blog", and the author recommended profanity, and lots of it. What is it about swearing that attracts so many people? Do you think people swear more or less than they used to? Do you swear more online than you do in real life?

I have to confess that bringing up young children made me change my habits quite quickly when they became verbal. Nothing is worse than having your child be the one to teach the other preschoolers a bad word. Oh the frosty glares from the other mothers when that happens! Now that we've censored ourselves at home, it feels strange, and my husband and I cringe a bit, to hear people swear in public when we are with our kids. But when they are not within earshot it doesn't bother me.

(The other thing I noticed is that Lewis is not above swearing in his private letters to his brother.)