I have now read the Survey of Gangs report.  It is certainly helpful and at least, it lets me know I was not too far off the mark.  The report took about 3 weeks of research and is obviously limited by that.

The key points that I noticed/inferred are :

• the gangs have been around for quite a long time but had remained largely un-noticed (by the foreign community) until April this year

• there are many groups, most of which we might call youth groups – only some of these can be properly called “gangs” (if we associate violence or law breaking with the word gang)

• it seems to confirm that the east/west divide has been around for a lot longer than this year

• unemployment may well be the key reason for the huge membership numbers of these groups, but cultural and safety issues are not to be discounted

• more than 50% of Timorese men belong to one of these groups

• the study specifically identified 107 such groups but estimated the real number could be 3 times this figure

In the western world, we really have many groups that would come under a similar umbrella.  For example, sporting clubs, hobbiest clubs, singing, dancing, chess, even Rotary, but none of these tend to involve themselves in running amok.  We may only guess what might happen in our own cultures if unemployment blew out to 50%.  (The figure could even be a lot higher here than 50% as the percent of Timorese in classical wage and salary earner jobs is probably less than 20%.)
One thing you do notice here is the almost complete absence of sporting facilities, and I am nowhere near the first to say “send 10,000 soccer balls and give the kids something less destructive to do”.  Didn’t you know that western governments pump money into sport to allow the masses to expend energy on something other than kicking over rubbish bins (and governments) ?