[dsims]

What if they allowed duplicate names? Navigating to twitter.com/username would then display everyone with that name (like how Wikipedia handles it). The chances that you are following more than one person with the same name is pretty slim. If that does happen, then you pick which one gets your @ replies.

[johns]

I wouldn't want my competitors sharing a username with me.

[kragen]

Because you worry there wouldn't be a unique way to link to you, or because you don't want your potential customers to know who thinks they're your competitor, or because you're worried people would get confused?

[diN0bot]

that's a good point, but i bet that could be resolved, too. i like the show_all option. the more transparency the better. we still want to be careful not to squander the resources of clarity and lack of information.