What is the meaning of "Beauty and Folly are old companions"?

The origin of the phrase is Benjamin Franklin in "Poor Richard's Almanac" (1734).

http://usa.usembassy.de/etexts/funddocs/loa/bf1734.htm

One suggested explanation of its meaning is:

'This means be careful about getting by with good looks alone, it will eventually lead to problems, you must have substance behind the superficiality of good looks, in other words, beauty is as beauty does.'

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