Legitimately curious response: have you tried thinking through the answer to this question, and if so, what seems like the likely answer in your view? If not, why not?
So I'm not sure what question you're asking if someone has put thought into, but assuming it was "What do they hope to achieve by this?"
shakes Magic 8 ball
My guess is it's a combination of what the Sri Lankan poster above mentioned combined with a reaction to further technical escalation by the citizenry.
Unfortunately, there are too many unknowns w.r.t. Sri Lanka's government/cultural values for me to even hazard a guess as to what the endgame is beyond minimizing net driven attempts to organize.
What I do see potentially transpiring, however, is someone figuring out how to host basic net based communication within the country; odds are though, the government feel themselves sufficiently equipped to take down in country rabble rousing, and possibly aim to keep outside influences from inflaming things further.
Best thing you can do if you want to get out, is find the IP addresses for your particular of site, and use that. DNS based blocking does squat if you're maintaining your own registry of IP->Domain Name bindings. If they catch on and start trying to IP block, well, welcome back to the pre/early internet days. Hopefully you know someone willing to host you a forwarding proxy.
