There are so many charities and events competing for our support these days that you have to be selective in what you donate to.
I now not only base my decision on the charity but on the method of fundraising.
I've seen people pledge a skydive in return for donations to a charity or decide to walk the length of the country.
I'd consider sponsoring someone to do a skydive if they were genuinely terrified of heights, otherwise you're really sponsoring them to tick something off their bucket list.
The same can be said of walking the length of the county. If the person is actively raising awareness for the cause at the same time, I'd get behind it. Otherwise, you could likely donate just as much as if you kept working and donated all your earnings for the time it would have taken you to cover the distance.