It's called the "Fair Use Policy" which is a network defined policy which could change as they deem necessary.
Globe has presently defined it (which they could change anytime they wish) as a speed throttling whenever an "unlimited" plan which fell under their old rates would reach 1Gb per day or 3Gb per month whichever comes first for postpaid and 800Mb/day for prepaid.
Note that this could change without prior notice.
i agree with giefreak, hinde dapat tawagin na unlimited kung may limit lang na data na pwedeng magamit. at hinde rin pwedeng tawaging "fair usage policy" kung napaka-unfair naman para sa nagbabayad ng unlimited internet ngunit limited lamang ang data na pedeng magamit. sana po ay magawan ng tamang aksyon to ng globe. ty po and god bless