I'd say it depends on whether you know the person and what they did/accomplished in their life. For example if a well known person in my area that knew everybody died but I didn't like them that much, I wouldn't speak ill of them unless they had actually done some really bad stuff. As with MJ and Jade Goodie, Michael Jackson made a lot of good music in his life, sure he may have had a shady private life but in 50 years time, what are people going to remember? His music or his private life?
Jade Goodie on the other hand, as far as I know, never accomplished anything other than "winning" a reality TV show in which you basically sit around talking about nothing with some other random people once and then being featured on the same TV show again a few years later as a celebrity, only to get voted off because she made a blatantly racist and offensive comment. She was then diagnosed with and died from cancer, OK yes, someone dying from cancer is a tragedy and I'm not going to deny that but it was over dramatised and people really shouldn't have made such a big deal over her dying when thousands of others suffer the same fate and instead of leaving their families with millions of pounds from various media outlets, their families will often have to struggle on with nothing.
It didn't bother me as such when either of these two celebrities died although I felt that the death of Jade Goodie (and that she was portrayed as some kind of saint) was a 'slight' over reaction however people will joke about anything that happens to a celebrity, local or global so there's no real point in getting offended at it.