From the Windows Phone 7 Application Certification Requirements (section 4.6).
"Screenshots must only contain application graphics, and must not include any emulator chrome."
But then there are these: (images linked directly from the marketplace.)
These screenshots show a combination of browser chrome and developer frame rate (performance) counters.
Yes, I've seen lots more examples.
No, I don't think it reflects well on the Marketplace as a whole. :(
What would I like to see?
4.6 being more rigorously enforced.
and a new clause being added to the certification requirements that screenshots don't include performance counters.
Is that too much to ask for?