I wrote similar code for my photo sharing startup at least 5 years ago. Showing a photo's detail page and related photos based on tag and dates from that photo

I wrote similar code for my photo sharing startup at least 5 years ago. Showing a photo's detail page and related photos based on tag and dates from that photo is a fairly trivial task. I really don't see the big deal; surely others have done something similar. They just weren't Facebook! Now if someone had taken their name, changed a letter, then their logo and made it 3D, and them built a big brand around it, then I'd say go sue their asses off. But this? Seriously?