As far as the Flickr warning, for Firefox and IE, here are how to enable cookies:
Firefox- Tools > Options > Privacy > Cookies > Allow Sites to use Cookies
IE - Tools > Internet Options > Privacy > Advanced > Override Automatic Cookie Handling > First Party Cookies allow & Third Party Allow or Prompt (up to you)
So far I have never found cookies to be harmful. I run AVG or AVS antivirus and I scan with Ad-Aware every so often.
I have only just joined Photobucket yesterday and I have been using their online bulk uploading page and haven't had a problem (other than being damn slow).
I'm going to go look for this Flock program for bulk uploading though...I prefer an on computer uploader...much faster and more simple to use.