We used Twitter for language learning at the distant college of Shanghai Jiao Tong University. Our adult learners seldom have contact to native speakers and only few opportunities to practice English (and only limited time). So, we taught them how to use Twitter and "recommended" to twitter at least  5 times a week.

“This "TWITTER" same as schoolyard~~~”

“Would you please do not close the twitter online? It offers us a free space to put ourself in English.”