I agree,
"What about if your company is global in nature (Google, Microsoft, IBM, Salesforce, HSBC etc - ignore where head office is located)"
But it doesn't work like that...
Checking my local sites for those companies:
Google.com redirects to Google.com.hk
Microsoft.com.hk redirects to Microsoft.com
IBM.com.hk redirects to IBM.com
Salesforce.com.hk redirects to a (unrelated?) HK company, Salescatalysts.com
HKBC.com and HSBC.com.hk are separate sites, both run by HSBC
So, companies that are global in nature have to buy all the local domains, or risk their potential customers getting diverted.
What gets REALLY annoying is deliberately typing in the .com version of an address, getting redirected to the local site which displays in the local language that you don't understand (as opposed to the second official local language that you do understand).
It is a result of a combination of confusion:
1. "The Public" think website addresses start with http://www. and end with .com, anything else and you get asked "Do I need to add..."
2. Developers don't understand there is a difference between location and language (even when using GeoIP - when they are both just meaningless text to trigger a response in the user, see http://xkcd.com/713/)
Finally, marketers like the idea of having new TLDs to sell...