You don't need all your apps to always be installed, Installed apps, even when they are moved to your sd card, they still use a small chunk of internal phone memory. This internal memory usage adds up when you have a ton of 'installed' apps, until there is a low internal memory, too low to handle any extra tempoary caches that build up.
I keep most of my downladed apps uninstalled, backed up to the memory sd card. Using a 16 gb card leaves me lots of space, and backup with 'Android Assistant+18', there are other apps that do backup. This keeps the Optimus V's limited memory clear enough so I don't have low memory problems. And when I want to use an app, I can just 'restore' it, and when I'm done using that app, I uninstall it again. This method keeps 'annoying' apps that always respawn, or turn themselves on again after force stopping them, from using the phone's memory/data unnecessarily.
P.S. "File Manager" is a very good free app that also backs up. Dolphin browser now has an anti-virus add -on thats as good as anything I've used/seen.
12/16/2012: I would also suggest getting these free apps from the Playstore. Android Assistant+18 by Aaron, File Manager by Rhmsoft, Clean Master, and if your device is rooted, DroidWall.
Android Assistant has a lot of useful tools including an app backup and app to SD card utility.
File Manager is a very good app with no time limit like some other free file managers have.
DroidWall (for rooted devices only) is a nice little 'firewall' app that does not have any 'permissions. It lets you "whitelist/deny" internet access for any installed app. Works great! Especially useful for people who have limited data plans.
Clean Master cleans up caches and old unused data from your device.