With every new version, Yahoo! Messenger seems to be using more and more memory than the previous versions. With the addition of the Plugin feature in the latest version, things have got even more bulky.
Currently, Yahoo! Messenger uses about 41,164K memory on my system. Based on your usage of the messenger, the memory usage increases and decreases.
Here are some very simple tips to decrease memory usage of Yahoo Messenger:
The amount of memory Plugins use depend on the number of plugins you install. To uninstall plugins from the Plug-ins Manager, go to ‘Actions>Choose a plugin…’ and click the ‘My Plug-ins’ tab. Decide which Plugins you don’t need and then click ‘Stop’ and the icon near to it to uninstall
You can save some memory and bandwidth by removing Yahoo! Messenger’s Ads. You can find how to do it here
Switch to Classic Skin: If you prefer performance to appearance, you may switch to the classic skin of Yahoo! Messenger. You can do this by going to ‘Messenger>Change Skin…’ and select Classic from there.
Just little reference to reduce memory usage of yahoo messenger.