Never ever is such a finite thing to say. Multitasking, with a memory intensive game will put it over 4gbs easily. But, in everyday use it's rare to surpass 4gbs unless your a doing commercial work with big apps or files.
Intel I5 2500k 4.6Ghz@1.34v w/ Noctua NH-D14
Asus P8P67 Pro
OCZ Agility 2 60GB SSD
G. Skill RipJaw X 8GB 1600
EVGA GeForce GTX 560 Ti Superclocked
Creative X-Fi XtremeGamer Fatal1ty Pro
Thermaltake ToughPower 750W
Rocketfish Aluminum Full Tower Case
Asus P8P67 Pro
OCZ Agility 2 60GB SSD
G. Skill RipJaw X 8GB 1600
EVGA GeForce GTX 560 Ti Superclocked
Creative X-Fi XtremeGamer Fatal1ty Pro
Thermaltake ToughPower 750W
Rocketfish Aluminum Full Tower Case