About "Libyan Youth Movement"
They have a facebook page:
http://www.facebook.com/pages/Libyan-Youth-Movement/133738650025293
...it currently which has this message posted at c. 8.30pm (GMT) - '4 hours ago'
"OUR TWITTER ACCOUNT CURRENTLY HACKED, TRYING TO GET IT BACK sorry for the delay we have more urgent news to come out they have taken us off"
However, they have previously posted on the FB page that twitter is their priority at the moment, so it might be they have sorted out their twitter but not taken down the FB warning.
As for where they are located, if they are 'legitimate' and who is to blame for spreading rumours...
1) It is my understanding that there are activists inside and outside Libya who work together to get around internet shutdowns and blocking (for example youtube has been blocked in Liyba for 1 year already but they know how to use proxies to get round this). As I understand it people inside Libya use whatever methods they can (landlines, mobile phones, texts, email, etc) and then someone who actually has a decent internet connection, the technical ability to avoid blocking and is in a safe location can then upload, retweet, post to facebook and so forth. You have to remember that most people in Libya don't have internet connections, but mobile phones are more widespread. If mobiles and internet go down then some people have landlines. If landlines go down then a very small number of people have satellite phones (some European activists have been putting some in place prior to the recent protests in the region). No everyone has very good English, so there is a need for translation and re-posting. We havbe to make allowances for the very difficult conditions - far worse than Egypt - that Libyan protesters are operating under. For some they do not have the option of remaining in Libya as they would have been killed years ago, but they still remain in touch with their networks and contacts back home.
2) As to 'who they are' & 'are they genuine' - one good sign is that they have multiple connections with other pro-democracy activists, in terms of journalists and activists elsewhere who are following them and who recommend them (from long before this week).
3) Blame for spreading rumours: this is difficult - they want to transmit as much raw inforamtion to the outside world and within Libya to other protesters and the Libyan population as possible, however if they don't filter it or 'edit' it then they can end up re-posting rubbish/misinformation. Mainstream journalists often err on the side of caution, as they want to remain 'neutral' and 'professional'. Activists don't want to remain neutral, but they do want to remain credible. They also don't want to be tricked by their opponents - either spreading fear so that people don't go out, or being so optimistic and gung-ho that people charge strait out into a trap. In some sense this is raw "information warfare" going on - both sides are trying to trick, demoralise, outwit, mislead the other, to gain some advantage or to influence the wider population and outside powers.
Conclusion: we have to try and read everything that comes out in different channels, do out best to analyse what is plausible, which bits conflict with other bits, which bits have been confirmed elsewhere, what time/location/source they really come from etc. there is no point simply re-posting every single tweet we see (we might as well just read twitter instead). I have been trying to be selective and construct my own 'time line' of what is going on and where, try and make sense of it for myself, and then share my 'version' with others. It is not easy and I can't pretend I am that confident about what has actually been happening, what is 'chinese whispers' and what is downright misinformation.