I have not used this addon, I am writing this review to give users who find it installed on their system without consent some useful information.
This addon may suddenly appear on your system without your knowledge, in which case it probably came from a Skype update, which is what happened to me.
Some users are not able to uninstall the addon through Firefox's addon manager because the uninstall button is grayed out. This is not the fault of eBay, the developer of the addon, it is due to a bug with Microsoft's .NET Framework Assistant. The Framework Assistant is installed at the computer level, rather than the user level, in order that the .NET Framework be available to all users of the computer. It is due to a bug with this installation method which prevents the Browser Highlighter from being uninstalled through Firefox. You can find more information, as well as a downloadable patch on Microsoft's website here: http://support.microsoft.com/kb/951847
This addon is not installed without user consent by eBay. It is also not installed without user consent by Skype so long as the user is installing a NEW version of Skype downloaded manually from the Skype website. Those users who find it installed WITHOUT their consent had it installed as a result of Skype's built-in update feature, either automatically or manually. When using the built-in Skype update feature, the user IS NOT provided an opportunity to consent or deny the installation of the Browser Highlighter addon. This is the fault of Skype, not eBay.
For users running 4.1.x or older versions of Skype who do not want this addon installed, you should download and install Skype manually from Skype's website rather than using the built-in Skype update feature. Skype has REMOVED the Browser Highlighter from their installer in the 4.2 beta version of Skype, and I suspect that when 4.2 is released out of beta, it will not have the addon included either as a result of this fiasco, but I cannot speak on Skype's behalf, I only know that it has been removed from the Skype 4.2 beta installer.
This issue seems to have cropped up either in July or August of 2009, and why in that amount of time not one representative from either Skype or eBay have offered this information is beyond me. It took me under one hour of investigation to realize what happened and find all the information needed to fix it.
eBay, you could have done the same, trying a Skype upgrade, to see if indeed the user IS INDEED presented with an option NOT to install your addon, rather than simply posting reply after reply that the user HAS to authorize its installation and assuming they were idiots. This information could have been here months ago, and all these negative reviews could have been avoided for your product, and your reputation could have been salvaged. I couldn't care less why this did not happen, but for your own benefit, it needs to be brought to the attention of eBay management so that this sort of thing can be avoided in the future.
Skype will probably never see this, but you guys really dropped the ball by allowing this to continue for so many months. Even today, Dec. 28, 2009, if I search your website for either "browserhighlighter" or "browser highlighter" I get either a page that says there are no results, or a page that does not show any results AND doesn't say there are no results, which seems to indicate that you are filtering this issue away from your users and trying to hide it. That is BAD behavior if that's the case, every bit as bad as not presenting a user with an option NOT to install 3rd party software with an automatic update. Please ensure this is NOT the case, or your company may never recover.
This search for "browserhighlighter" returns no results and no message saying there are no results, indicating possible filtering and cover-up: http://search.skype.com/search?q=browserhighlighter&btnG=Search&entqr=0&output=xml_no_dtd&sort=date%3AD%3AL%3Ad1&client=forum_default&ud=1&oe=UTF-8&ie=UTF-8&proxystylesheet=forum_default&site=collection_forum
This search for "browserhighlighters" returns no results but DOES return a message indicating there are no results: http://search.skype.com/search?q=browserhighlighters&btnG=Search&entqr=0&sort=date%3AD%3AL%3Ad1&output=xml_no_dtd&client=forum_default&ud=1&oe=UTF-8&ie=UTF-8&proxystylesheet=forum_default&site=collection_forum
Cover-up? You decide.