In mid-June 2010, Google added blue dots to its maps that display user-submitted images, those blue dots seem to have disappeared for many Google Maps users.

You can still play with them over here but within the Google Maps user interface, for some, those blue dots are gone.

Daniel, a Google Maps representative, said he is aware of the issue and looking to fix it. He said in a Google Maps Help thread:

Here is a picture of what they may look like:

There is no ETA for a fix.

Forum discussion at Google Maps Help.