I've never heard of people wearing a ribbon because someone died, though supporting a charity for the cause of someone's death can be a way of helping to grieve, but (afaik) it's not the main reason the ribbons exist. I believe they're all supposed to be to raise awareness of a condition / charity / problem.
Also, awareness raising does not have to be about a cure (though in the case of AIDS, cancer, etc. a lot of the funding from the charity can go into research)... A lot of awareness raising can be going to how to help people with a problem, how to recognise a problem, etc.
[Edited to add: It appears that the Autism Society (http://www.autism-society.org/) are the source of the puzzle ribbons. It doesn't appear that "researching a cure" is on their list of projects, but raising awareness, support for people on the spectrum and support for familes of those on the spectrum are high on their list.]
I support raising awareness about autism / AS and the more people who see something and ask a question and get a sensible answer, the better...
I didn't know there was an autism ribbon, but will get one now... Therefore if anyone asks me what it's for, I can say it's to raise autism awareness and hopefully a discussion about what autism is, can take place and one more person will be a little less prejudiced to someone who, to them, is a little different...