Death On The Installment Plan

A "Blogger" pled guilty to manslaughter after he confessed in his blog:

"It was me who caused it. I turned the wheel. I turned the wheel that sent us off the road, into the concrete drain ..." Ranking wrote in the blog. "How can I be fine when everyone else is so messed up?"
(...)Blake was sitting in the back seat as he and then-17-year-old friends Jason Coker and Nicole Robinette left a party when he pulled the steering wheel as a prank, causing the car to somersault off the road.

There are other cases where Bloggers committed crimes then wrote about them. Most infamously the case of Rachelle Waterman, who kept a Live Journal, and conspired to kill her mother.

Another Blogger wrote a last blog entry that led police to the man who murdered him.

A doomed Queens man's chilling computer entry led cops to a suspect who allegedly robbed and killed the victim and his sister to finance a return to China, police said yesterday.

Jin Lin, 23, was charged with first-degree murder yesterday in the bloody slayings of Sharon and Simon Ng in their Kew Gardens Hills apartment Thursday, officials said.

Cops zeroed in on Lin, who once dated the woman, because Ng typed a journal entry into his computer fingering his sister's ex-boyfriend as the suspect, police said.

Of course, there are also blogs that seek to unravel crimes, such as, the murder of the blogger's sister.