Yesterday, I attended a public workshop here at the Googleplex entitled "Quick & Dirty KML Creation". Pamela Fox and Mano Marks showed us "how to use tools within Google Maps and Google Earth to create, import, and edit KML." This was part of the Google Geo Developer Conference series.
The presenters described using Google Earth and MyMaps feature of Google Maps to create, edit, import and export KML. They also discussed the new KML spreadsheet tool that allows you to create placemarks using entries in a Google spreadsheet, the Google Maps API and other topics.
One participant asked an great question: when should you author content in Google Earth as opposed to editing the KML directly? Generally speaking, it depends :-) For example, editing in the Google Earth graphical user interface (GUI) is optimal when you are creating a specific view, or want to visually choose colors and icons. But editing the KML itself is best when you are creating single shared styles for multiple items, or add in elements such as time animation that the GUI interface doesn't allow you to edit.
This workshop should be available on YouTube soon. I'll post a link for it as soon as possible.