Impact of Facebook Like button on images

At Elasticera we have known for some time that Facebook makes a huge number of image requests on a daily basis.

The following graph shows what % of Bot requests Facebook accounts for across all of our customers.

A surprisingly high percentage. However this does not tell the whole story. Not all of our customers use Facebook Like buttons with their product images.

The following graph shows what % of Bot requests Facebook accounts for with a customer that uses Facebook Like buttons with their product images.

Facebook could save websites and themselves an awful lot of bandwidth / CPU cycles if there was an attribute for the image tag.
 
For example

<img class="rounded" src="blah.jpg" hash="SHA1-of-image">

Facebook could then send the hash with the Like request and if Facebook has the image with that hash it does not need to request it.