Stock apps are the applications installed by default when you buy a branded phone. Most of them are useless, not optimized and have open source alternatives that can protect your privacy.
JUST REMOVE THEM.
Below, for instance, are listed ring files on my Xperia X10 Mini. Just look at which ones are the largest : Sony Ericsson and SFR (carrier)…
# busybox ls --color=never -lS /system/media/audio/ringtones
busybox ls --color=never -lS /system/media/audio/ringtones
total 2977
-rw-r--r-- 1 0 0 643902 Jan 19 2011 SFR_Ringtone.mp3
-rw-r--r-- 1 0 0 206809 Jan 18 2011 CrazyDream.ogg
-rw-r--r-- 1 0 0 175423 Jan 18 2011 DreamTheme.ogg
-rw-r--r-- 1 0 0 150152 Aug 18 2010 sony_ericsson.ogg
-rw-r--r-- 1 0 0 59024 Jan 18 2011 Ring_Classic_02.ogg
-rw-r--r-- 1 0 0 54923 Jan 18 2011 Glacial_Groove.ogg
-rw-r--r-- 1 0 0 52809 Jan 18 2011 Ring_Synth_02.ogg
-rw-r--r-- 1 0 0 52536 Jan 18 2011 Revelation.ogg
-rw-r--r-- 1 0 0 50578 Jan 18 2011 Eastern_Sky.ogg
-rw-r--r-- 1 0 0 49978 Jan 18 2011 GameOverGuitar.ogg
-rw-r--r-- 1 0 0 49108 Jan 18 2011 Road_Trip.ogg
-rw-r--r-- 1 0 0 46673 Jan 18 2011 Big_Easy.ogg
-rw-r--r-- 1 0 0 46425 Jan 18 2011 FriendlyGhost.ogg
-rw-r--r-- 1 0 0 46049 Jan 18 2011 Thunderfoot.ogg
-rw-r--r-- 1 0 0 44422 Jan 18 2011 Seville.ogg
-rw-r--r-- 1 0 0 43965 Jan 18 2011 Ring_Synth_04.ogg
-rw-r--r-- 1 0 0 41828 Jan 18 2011 BirdLoop.ogg
-rw-r--r-- 1 0 0 41094 Jan 18 2011 Growl.ogg
-rw-r--r-- 1 0 0 39921 Jan 18 2011 Champagne_Edition.ogg
-rw-r--r-- 1 0 0 39738 Jan 18 2011 Funk_Yall.ogg
-rw-r--r-- 1 0 0 39413 Jan 18 2011 Shes_All_That.ogg
-rw-r--r-- 1 0 0 39199 Jan 18 2011 Paradise_Island.ogg
-rw-r--r-- 1 0 0 39174 Jan 18 2011 Bollywood.ogg
-rw-r--r-- 1 0 0 39138 Jan 18 2011 Savannah.ogg
-rw-r--r-- 1 0 0 39025 Jan 18 2011 Noises2.ogg
-rw-r--r-- 1 0 0 38875 Jan 18 2011 Calypso_Steel.ogg
-rw-r--r-- 1 0 0 38688 Jan 18 2011 Gimme_Mo_Town.ogg
-rw-r--r-- 1 0 0 38307 Jan 18 2011 LoopyLounge.ogg
-rw-r--r-- 1 0 0 37847 Jan 18 2011 Steppin_Out.ogg
-rw-r--r-- 1 0 0 37672 Jan 18 2011 Cairo.ogg
-rw-r--r-- 1 0 0 37179 Jan 18 2011 Club_Cubano.ogg
-rw-r--r-- 1 0 0 36620 Jan 18 2011 Terminated.ogg
-rw-r--r-- 1 0 0 36539 Jan 18 2011 Third_Eye.ogg
-rw-r--r-- 1 0 0 36287 Jan 18 2011 Noises1.ogg
-rw-r--r-- 1 0 0 34864 Jan 18 2011 MildlyAlarming.ogg
-rw-r--r-- 1 0 0 34627 Jan 18 2011 LoveFlute.ogg
-rw-r--r-- 1 0 0 32933 Jan 18 2011 No_Limits.ogg
-rw-r--r-- 1 0 0 32640 Jan 18 2011 OrganDub.ogg
-rw-r--r-- 1 0 0 31641 Jan 18 2011 RomancingTheTone.ogg
-rw-r--r-- 1 0 0 31563 Jan 18 2011 EtherShake.ogg
-rw-r--r-- 1 0 0 31136 Jan 18 2011 World.ogg
-rw-r--r-- 1 0 0 30925 Jan 18 2011 CurveBall.ogg
-rw-r--r-- 1 0 0 30759 Jan 18 2011 BentleyDubs.ogg
-rw-r--r-- 1 0 0 30615 Jan 18 2011 CaribbeanIce.ogg
-rw-r--r-- 1 0 0 28898 Jan 18 2011 SitarVsSitar.ogg
-rw-r--r-- 1 0 0 28691 Jan 18 2011 VeryAlarmed.ogg
-rw-r--r-- 1 0 0 28433 Jan 18 2011 BeatPlucker.ogg
-rw-r--r-- 1 0 0 28124 Jan 18 2011 MidEvilJaunt.ogg
-rw-r--r-- 1 0 0 26662 Jan 18 2011 Noises3.ogg
-rw-r--r-- 1 0 0 26298 Jan 18 2011 TwirlAway.ogg
-rw-r--r-- 1 0 0 26144 Jan 18 2011 SpringyJalopy.ogg
-rw-r--r-- 1 0 0 21007 Jan 18 2011 Ring_Digital_02.ogg
-rw-r--r-- 1 0 0 15563 Jan 18 2011 NewPlayer.ogg
-rw-r--r-- 1 0 0 15146 Jan 18 2011 InsertCoin.ogg
If you are really lucky you might be able to remove them completely with a command from ADB shell like : rm /system/app/facebook.apk && rm -r /data/data/com.facebook.katana.
With less luck you should still be able to deactivate them.
Otherwise, each phone has unfortunately different procedures… I wish you good luck…