The SysTray area on the Startbar is reserved for applications that want to notify the users about some state of the application.
A whole lot of applications , vying for eyeballs like all those portal startups of late 90s, end up misusing systray leaving behind a redundant piece-of-junk icon.
Here is a snapshot of the systray on my laptop. 42% of the icons should not have been there.

(1) Outlook new mail icon - indicates thatI have a new mail in my inbox, could have easily shown how many
(2) The main Outlook icon. Only distinguishes between online/offline. Should have shown connection error, send-receive status, out of office etc
(3) Pen Flicks icon being used just as a shortcut to access other menu items. Should not have been in the SysTray at all
(4) Protector Suite icon for the application that controls the biometric input on my Toshiba wasting useful real estate on my SysTray
(5) The extremely handy and well designed battery staus indicator that shows if my laptop is the approximate battery power
(6) Connectivity indicator shows availability of internet and LAN connection
(7) Volume icon: Shows mute/unmute - wish it showed me te volume level as well by using the green sound wave metaphor like the nokia bars
(8) Smantec AnitiVirus - Could easily have shown the health of my system by adding a simple Green Tick for a clean system, a Red swoosh if it found a virus or a suspect file and a rotating gear when a scan in progress
(9) V 9.2MOH model which currently is "on hold" but the icon tells me zip
(10) Windows Defender currently showing that it has blocked programs at startup using a familiar metaphor
(11) Acoustic Silencer for CD/DVD which can either be in normal or quite mode though the icon is non-resposive to the change
(12) ISA Server icon distinguishes its state of connection with the proxy server
(13) Windows Messeger shows a unique icon for each one of the states that messenger can be in
In short, a simple mesage to the developers: If you decide to put an icon on my SysTray, please take the pains to use the icon to indicate some state, else put the icon on the desktop