I remember one tale from Dave's of a poster getting in trouble with his public school for his travel blog. Alas I do not remember the details and the story is gone from the site. Tried google cache but nothing.
Another Korean blogger hassled for blog post in Brian in Jeollanam-do his was more hassled by a reporter.http://briandeutsch.blogspot.kr/2010/04/investigated-by-immigration-over.html
Korea is also strange with libel and defamation laws. Some strange things go on here with privacy. My recommendation is do not tell about your blog to coworkers. Use an alias. Try to make sure no email or name can link to your real name. Do not publish real names, use nicknames for school and location. That is why Facebook can be so dangerous at times. Most people are complete visible name wise. Check and adjust your security settings.
Some strange things you will notice with photos and video. Many Korean shows will fuzz out images of people. The ironic part is many waygooks are photographed and not fuzzed. Waygooks are less likely to notice or complain. You will see more of the hypocrisy during the summer. Waygook cover in mud at festival take picture. Korean Person do not take picture. Ohh good looking foreign girl no problem take a picture. Korean in bikini (tsk, tsk) still no photo. You will notice some photographers hanging out at the beaches in the Summer and they are likely not their for swimming. My point is you have some cute photo of your students. Decide to post them up. 99.9 percent most likely things are fine, but that one crazy mother finds out and they will rant and scream and threaten. I would post photos but avoid posting personal details like true names or school.
If you piss off the wrong person, they will find any reason in which to fight with. That is what I think happened with the above travel blog guy.
One piece of luck is Korean citizens are less likely to use Western sites. They usually keep to their Naver and Daum. Through that is changing as more and more Koreans are checking out twitter and facebook. If you want to interact with Koreans and they ask for email or facebook page you may consider a secondary/work account. One to give to students, parents, and those people you want to keep at arms length.
Hope that helps.