OK – so it looks like this is something new that Google has added. Earlier Google only had the “All requests per day” limit of 10000, which counted how many API calls you made. Photonic has control over that, and unless you are reeling under a DDOS attack you wouldn’t face an issue with it.
But it looks like now Google has introduced a new category called “Base URL requests per day” set at 75000. As per its documentation:
The quota limit for requests to access media bytes (by loading a photo or video from a base URL) is 75,000 requests per project per day.
So each photo you access counts towards this limit. If you show 100 photos in a page and reload the page 10 times you incur 1000 of your calls in this category.
That would mean that your guess about trying to load too many images causing this issue is mostly correct. Google cannot return more than 100 photos in one shot, so Photonic will curtail your count
parameter at 100 even if you pass a higher number. But each time you click on “View More” you start adding up the hits.
This is quite frustrating as Google happens to have the most restrictive policies among all photo sources – no more than 50 albums or 100 photos returned in a single shot, and now each photo counts towards a limit. None of the other photo sharing services does this.