My understanding of the term "sharrow" is the same as Thorn's.

I ride shoulders similar to what is shown in your picture, most unmarked as bike lanes. For the most part, there are no issues. The only time that it gets sticky is when a turn lane pops up and abruptly ends the shoulder, and then resumes on the other side. Our local bike advocacy group is working to address this issue with some selective painting to warn cars and to protect cyclists' legal rights.