[plonh]

A commenter explains that the most interesting claim (51% bias) is not explained correctly in the article. Humans flipping a coin add a bit of precession (spin) that biasses the toss. The "odd/even time in the air" analysis is incorrect -- that only matters if it is possible to stop the coin before the first flip.

[letstryagain]

Yep. To see this, consider a coin flipped into the air so that it's tilted 45 degrees with the floor and spinning only around the vertical axis. To a casual observer it will appear as if the coin is tumbling but in fact one side faces up 100% of the time.

[thret]

This is a trick that can be learnt with practice. If you spend a lot of time around gamblers, don't ever accept a coin toss proposition.

[jahnu]

Doesn't the person not tossing the coin get to call though?

[letstryagain]

If you call tails, I catch the coin and show it to you. If you call heads, I'll catch the coin and invert it before showing it.

[jahnu]

Ahh right. People I know usually call after the flipper catches and covers it. So they would have to have some technique for flipping it as they raise their hand to reveal the coin. Difficult but I guess not impossible.