I was really interested to find an article about voiceovers as a few years ago I was paid to be the voiceover on promotional CDroms for the Xter train here in France and the storage silos at la Pallice. Not very glam I admit, but I got paid well. With the voiceover for the train I was told afterwards that I had carried my work out more professionally that the French actress they used for the French voiceover.
A lot of singers can use their talents successfully in a voiceover They have the benefits of special training in voice control and can really use their speaking voice better than they might think. If they have experience of recording techniques they are at an advantage.