I think you will find the moveon dot org is taken a bit more seriously than you might think, Nicole. If you go to their FAQs page, scroll down and read about What is a Flash campaign, you will see that they do more than just collect signatures online.

Through grassroots volunteering, they hand-delivered over 200,000 signatures to over 400 individual congresspersons' offices. Those were hand-delivered by constituents of each congressperson's district; they would ignore them at their re-election peril.

As well, petition gathering was also followed up by thousands of volunteers phoning their congresspeople. From what I have seen, moveon dot org has a legitimate, well-established voice which is respected and heeded.