The ‘Memory Effect’ is a phenomena exihibited primarily in NiCad & to a lesser extent, NiMh batteries. The proper term to use is ‘Crystalline Formation’. Quote from batteryuniversity.com:

“Crystalline formation occurs if a nickel-based battery is left in the charger for days or repeatedly recharged without a periodic full discharge. Since most applications fall into this user pattern, NiCd requires a periodic discharge to one volt per cell to prolong service life. A discharge/charge cycle as part of maintenance, known as exercise, should be done every one to three months.Avoid over-exercising as this wears down the battery unnecessarily.”

Now we see that Memory Effect is repeated LACK of deep discharging, causing crystalline formation in a nickel based cell.
Li-ion & Li-po’s do not suffer from this effect, in fact they suffer from quite the opposite, as Ross posited above. Quote from batteryuniversity regarding lithium based batteries:

“Similar to a mechanical device that wears out faster with heavy use, so also does the depth of discharge (DoD) determine the cycle count. The smaller the depth of discharge, the longer the battery will last. If at all possible, avoid frequent full discharges and charge more often between uses. If full discharges cannot be avoided, try utilizing a larger battery. Partial discharge on Li-ion is fine; there is no memory and the battery does not need periodic full discharge cycles other than to calibrate the fuel gauge on a smart battery.”

So we can see that with nickel based batteries, full, deep discharges are GOOD, and with Lithium based batteries, full deep discharges are BAD.