The "To" field should not be blank when clicking a SMS link.
While testing the Evo 4G with a mobile web site that I’m developing, it was discovered that SMS links are not correctly handled by the Evo’s web browser or stock text message application. While the links will open the text messaging application on the Evo, the “To” field is simply left blank. The intended behavior should be to automatically fill in the “To” field with the phone number indication in the link.
The test link below will demonstrate this behavior, and should work for other mobile devices besides the Evo:
Edit: My post on XDA Developers regarding this issue.