Just saw this tweet 24 hr ago from @mattjuniper and it immediately got my attention. The 20% text rule has often resulted in ads getting disapproved even when the actual text (not grids) is less than 20% of the image.

Following the tweet, it took me to WeRSocial's blog Following the tweet, it took to WeRSocial's blog http://wersm.com/has-facebook-finally-removed-the-20-rule/ 

Without rehashing the linked blog content, what's really interesting is that Facebook will not prevent ads with more 20% text from going live. Instead, content would be categorized into:

• Image text: OK – you ad image contains little or no text

• Image text: Low – your ad’s reach may be slightly limited

• Image text: Medium – your ad’s reach may be limited

• Image text: High – you may not reach your audience

So, much text should go into the ad and is the first quadrant [Image text: OK] = 20%? Probably, but Facebook would not want to explicitly mention the percentage as it would mean all content creators rushing towards 20% (or higher/lower) when there's so much context that will determine a photo post's final reach.

From an media perspective, this would definitely impact the Cost Per Reach / Cost Per Engagement metrics as brands would have to choose visual content that has just enough text to retain user attention. 

This change seems to have been applied to UK/Ireland only [for now] http://adigitalboom.com/update-facebook-removes-20-text-overlay-rule-for-ads-uk-ireland/