I've Noticed there have been a lot of small companies (and attractions) being Marked in on Google Maps and Google Earth in recent Months
I have found out how this is Done on Google Maps ,But unsure how to do it from Google Earth
The Process is Very easy to do and you can have a Marker Placed in seconds
And on the same page you can Make a custom Map for Private or Public Viewing
( Both Very simple even for Newbies to Google Maps)

Method:
Open Google Maps Disregard the Map Look in the left window

There are 2 Links here, disregard the Lower Link. Its for Placing Ads
The Upper link says: Put your business on Google Maps

Click this, this will take you To this Page which has a short Video showing How to Set up the Link (You have editorial control all the Time) Labelled "Google Local Business Center"
Need a Google account = Gmail address to use this feature
I was unable to get a UK English page for this
I tried and ended up on the Australian Google staff Blog!
A good introduction to Placing/editing your Marker is to Make up a Private custom map
Go back to the Link window
Click on My Maps then the Create New Map link on the Top of the Link lists
Several examples of what can be done and You can use them in the Usual way with Streetview if available?
Ps The Link Notes are also displayed in the Left frame So you can edit from Either side.Map edit buttons consist of an Icon Placing selector and a Line drawing button
To change the Icons over and Edit
you can click on the link in the Left frame or click the icon Link for a Message box.
To change the Icon Click the icon pic (its a button) The selection is very basic
Made a Mistake and want to delete ? The Delete link is in the left bottom corner of the Box.
Be aware that the custom Maps can all be displayed together (Tick box links on left to filter these)