yes the problem may arise if you are working in a company with these boundation or a country like dubai where the UAE goverment has banned these sites same as china govt also banned twitter in their country.
you need to think any other way to access and update your status. yes there are many ways and at Redefining technology (techmadly.com) we already discussed some ways to access blocked website and here we are giving some more ways to access the same:
1. HELLO.TXT :
this site just works as a bypass site you just have to sign in in this site with your twiiter nick name and then Goto->dashboard where you can find the option to update the messages.
2. GTalk Update:
if you are able to access your gtalk then only thing you have to do is just add firstname.lastname@example.org as a contact. after adding just type the message you want to update in your twitter timeline.
you can also use proxy site to access your twitter updates and this article at techpavan.com will help you in accessing that way.
if you are also not able to open your gtalk then the browser based version of gtalk will definately be your help. just followe the link http://talkgadget.google.com/. and then follow the procedure of step 2.
so if you use any one of the above for accessing your twitter then let us know how it works for you share your experience with us.