Because I have a certain profile as a Japanese person who happens to write a lot in English about things Japanese, I periodically get asked to support this or that cause or organization related to Japan.
Unfortunately, my time and physical resources are limited at the moment (see previous entries here for specifics). I have supported several fundraising events, charitable organizations and such since March 11, and continue to donate my personal funds in one way or another. (Not that you need to know that of course. I'm not doing it for acceptance by the internets.)
Regarding overseas organizations, I will only promote a group or cause if there is a clear indication that that it is working directly with a Japanese group or organization. I do not give shout outs to groups who are only working with non-Japanese groups or organizations. The reason? My feeling is that you cannot know the true needs of a country unless you are working with the people of that country. (International aid organizations such as the Red Cross or Doctors Without Borders already are working with people within Japan, so that's fine.)
This is not limited to charitable organizations. For instance, if you're part of a group that wants to measure radiation in Japan, but you're not working with a Japanese organization in any way (and there are plenty of them already probably doing what you intend to do) then sorry, but I think you're going about it the wrong way and so you won't be hearing from me.
So if you send me an email or a Twitter asking me to promote your cause, and I am silent, that's probably why.
Thanks for your understanding.