I used this activity in a 9th grade class of English Language Learners to assess how well they were grasping the grammatical concepts that we had covered that week. For example, we were working on subject-verb agreement using the "be" verbs "is" and "are" earlier in the week. Using this handout, I drew a picture of myself in the box under the "Facebook" logo, and then I created a status update that contained six "be" verb usage mistakes. The students' assignment was to first circle/highlight the six mistakes in my status, and then they were to tell me why they were mistakes in the "comments".
This activity was easy to differentiate because I would have my lower-level ELLs attempt to rewrite the sentences correctly, and my higher-level students would have to point out the mistake as well as rewrite the sentences.
The kids really liked this activity because of the relevance of Facebook in their lives, and I think it would work well as a grammar exercise in the Middle School levels as well.
This activity is also a super flexible in that you can change your "status update" each week to reflect the various grammatical/structural skills you are working on with your students.