.us is the only one of those extension that is safe to invest in.
I mean its the country code for usa, it will only up in value.
.mobi I dont really know about this one, its a shot in the dark, it could be WORTH ALOT IN THE FUTURE... but its most likely to be WORTH NOTHING, but it has BIG COMPANYS BACKING THAT SHIT UP so who knows. the thing is normal extensions websites can be programmed to be used in telefphones too, so its kind of meaningless. but who knows really... internet is growing all the time. in 5 years, who can tell...
.Info... i mean isnt most websites about brining you info about a company, product, person etc anyways?... i dont really like it.
.biz Its like a F-version for a company that really would have liked to have the .com or country code instead, or net, org or whatever i guess we'll have to take .biz after all, we want to be on the net dont we?
.me I think its a good domain hack for words like, love:me kiss.me fly.me drive.me hate.me promote.me etc...other than that, i dont like it at all.
.ws i dont have a clue what that is...?