Is taking his picture legal?

I take pictures of people all the time when I travel (around the world), and post them on my travel blog.

I also see other's pictures with people in them.

How does one take a picture in a sports stadium (or any public place), then ask all the people if it's okay to post their picture?

In Us, if you had published them (for money0, you'd have to have a release if it clearly depicted their features.

In Canada, sports stadiums are generally not public places as they are privately owned. The backs of tickets generally tell you whether or not you are allowed to take photos for anything other than private use. Some are very clear that no photography at all is allowed, others allow it for your own viewing (but not posting/blogging), others allow photography and posting - but not for $. Definitely worth checking the ticket back and the publicly posted rules upfront so recording equipment isn't confiscated.

Even some public places here do not allow photography. A friend, her hubby and child were kicked out of a public pool this summer as she was taking photos of them - big sign said no photos. They were told they could leave - or hand over the camera. Yikes.

It's probably a good thing I'm "slowing down" on my blog. However, with almost 35,000 hits from around the world in three years, it's an accomplishment I never would have dreamed of. Enough is enough!

Generally yes. Public spaces aren't restricted unless the person is under 18 and you're going to exhibit the photo or film publicly (as on tv shows. Then you either need to blur the identity of the minor, or get a signed legal release to use their image for commercial purposes.) But in the case of 'just some guy standing around' it's legal as far as I know.