- Without being to specific... What kind of organisation are you (how 
many people, nationalities, professions, (fe)male, age, ... an 
average maybe)?
from 15 (neg) to 26 (me), add yourself if older :P

- Are you all Belgians?
those participating in the protest, yes. the Anonymous movement itself is a worldwide happening.

- Do you have contact with other anti-Scientology organisations?
anonymous has been in contact with alot of anti-scientology organisations (eg. Mark Bunker from XenuTV) and ex-scientology people (eg. Tory Christman). 
+ add about contact in belgium if any

- How did you find each other?
blabla about youtube video's from anon and finding eachother on the central IRC network used to coordinate everything.

- Where does your motivation come from?
scifags suck! ;-) the whole shebang.

- Scientology probably knows you exist, did you already have bad experiences with them?
not personally, but we have seen video's of other people's experiences with them, such as Mark Bunker (XenuTV) and John Sweeney (BBC). several testimonies from other ex-sci can be read online.

- Did you ever meet their battery of lawyers?
see prev q

- Scientology continuesly pretends to do charity-jobs, like their 
famous anti-drug-program at schools. Do you think they lie at that 
point? Do they have a 'hidden agenda' to find as much members as possible?
every organisation ran by Scientology has the sole purpose of leading people into Scientology. perhaps talk a little about the companies scifags have in belgium ?

- The protest of Sunday seems to be the first big manifestation 
against the mouvement, how many people do you expect and why in 
Brussels?
brussels = scifag hq, only for belgium. 250 locations worldwide.

- I always understood Belgium was nog a good 'base' for Scientology, 
the number of members here stays low. Is that correct or is the 
threat bigger than everybody thinks?
no idea :|

- I suppose you are aware of the juridical investigation of the 
Public Ministery of Brussels (officer of inquiry: Jean-Claude Van 
Espen) against Scientology. Justice is making a case out of it. Why 
do you still stay anonymous, how do you see your role in this story?
We want to educate the public and raise awareness as well as interest in the upcoming lawsuit to provide popular support to our ministry of justice.

- You stay anymous for absolutely understandable reasons, but do you 
think this is the way to fight them? Because they always send a 
spokesman out if there's a conflict and pretend to be open and 
transparant.
This is pretty much unimportant in the bigger picture. 4000 (registered) people (so probably alot more) doing 250 protests worldwide will raise mass public awareness. Anonimity is not a problem in this matter.

- Last question so far: why the red tie (cfr. dress code) Sunday?
LOL.