On a whim, I ran off to Amazon.com and picked a couple of self-professed self-published authors I found on the “Indie authors self-promote your kindle e-books here” thread.
It interests me that even though ebooks have no physical form, the cover is still a vital piece of promotional material. However, it has to work at thumbnail size. If the cover and title interest you enough, you click on the icon to take you to the book’s page. This page includes traditional cover elements like a book description (the blurb), but also includes more information than a traditional cover (reviews, links to the author’s website, etc.).
Hot Tea by Sheila Horgan
This is a quirky cover design, but the typeface of the title is hard to read, especially at thumbnail size. This is partially mitigated by the fact that Amazon.com lists the book title next to the image in easy-to-read type.There's also not enough contrast between the type and the background. There's also something amateur-ish about the cover photo.
Maximum Discretion by Paul A. Fielding
The book title for this novel is nearly impossible to read. Since the title is the main feature of this cover, the fact that it's not readable is a major problem. It also interests me that the author’s name is being presented as the most important information on the cover, which seems unlikely as the lack of reviews for this book suggest that it is not a well-known author.
Updated 4 July
I also have to add this self-published cover in here because it illustrates the importance of not distorting images when re-purposing them to electronic format.