CSS styling conflict prevention and namespacing techniques

I would prefer to use a combination of the two solutions like:

.awesomewidget > div ul li {}

Because the second one adds a LOT of unecessary weight to the markup.

Update

For your example, I would add a wrapper around the user content with class .user and then prepend their CSS with .user. However, this is not graceful, it adds some markup, and I think it would be prone to failure.