Flickr will soon gate access to the full-size versions of the images they host unless you have a paid Pro account. Fortunately, images tagged as public domain (CC0) or with a Creative Commons license are exempt from this change.
If you use Flickr to capture the results of your field surveying or preserve the memory of OSM meetups you’ve been to, this would be a good opportunity to double-check that it has the license you expect, especially if you’ve been linking to these images from OSM using image=*. One possible explanation for this change is increased demand from Web scrapers (a problem OSM is all too familiar with).