I would definitely not cap the posts, nor would I limit in any way their consumption. If I have something to say, why should I not be able to? And if I am interested in what someone does, I don't want to wait for a week to read it.

That said, it is important how the posts are presented. A person who posts all the time about each plate of food... might not be as interesting as another friend who writes only once a month, but usually about really interesting things. A good UI which puts control in the hands of the consumer (but easy to use - convenience matters) is the most important thing here imho.

Best of luck!