In order for homeschooling to be effective it takes a particular kind of child and a particular kind of parent. If the child is an average teenager who has a decent social life, does okay in school and is not super motivated then it is not (usually) a good fit. My reasoning is that the student will not have the learning environment that a school offers to push them to succeed.
However I've also worked in a facility that did truancy and I've seen parents who didn't want to go to jail because they didn't ever make their kid go to school and their kids were just left on their own during the day for the most part. These parents would "home school" but I wouldn't say anything was actually taught.
There are definitely some good programs out there, even if the parents aren't necessarily prepared to do all the teaching themselves, and I honestly believe that homeschooling can be done in a beneficial way. It can also be very isolating, painful, and result in a sheltered, unsociable semi-adolescent adult. There are plenty of comparable evils to the American public school system as well.
I went to public school for all 12 years, my siblings were in private school until grade 2 or home schooled. I honestly feel there has been no difference except they didn't waste time on bullshit and got things done quicker than I did. If I was homeschooled I probably would have only spent 3-4 hours a day on schoolwork opposed to 7. The only issue is my little brother is an entitled 10 year old who needs someone to pick on him to get him set right.