Plaxo in particular is extremely assertive at protecting its reputation and appears to regularly trawl the web looking for sites critical of their application, or alternatively is very keen to address concerns of potential users in a transparent fashion. within a week of publishing this article - you can read Plaxo's response at the bottom of the page.] Let's assume that you are reading this article because you are technically savvy - you are probably a webmaster, a corporate mail administrator or work in IT support.
When I update my contact details you will see them in your address book. Please take a moment to update your latest contact information.
Your information is stored in my personal address book and will not be shared with anyone else. Both these services involve a downloadable application for your PC connected to a web server back-end.
There is no evidence whatsoever that these applications use any underhand technique to install themselves on PCs.
This means that if you find Plaxo or Bebo on a computer, then the user installed it themselves (despite whatever protests they may make that they haven't been installing unauthorised applications). When evaluating free software this is the first question you should ask.
All seamlessly, in the background, securely in the cloud.