[rorrr]

If every combination is taken, you might have some legal problems with trademarks.

If you register something.io, and they already took something.com, there's a good chance

1) They are in the same business selling "something"

2) They were there before you

3) They might have registered the trademark "something"

If they decide to sue you, you will probably lose.

It also might be hard to market .io to non-tech people, pretty much everyone expects .com (.org and .net are alright, but not great either).