If you post too much on user walls(including your own), it will not allow you to post anymore for the remaining hour.
Every time I'm told that I've posted enough wall posts for the hour, I look at the clock and it's always x:57 every time. So it's 3 minutes until I can post again. Lol. xD
This is from Indigo's profile, thank me for digging it out of there.
However it is pointless, wastes space, and if you do it too much you won't be able to post on walls for the rest of the hour.
From Sempiternus' answer on this question.
This is my evidence I guess, two experienced users stating so.