Which could actually be a long-term weakness of the model, if the site grows too much too fast - with such a low cap on maximum points, it strikes me as possible that some channels and tags get way clogged if a sudden influx of users with a different value set than the past core demographic show up. Personalized feed won't be affected by this, ignore and the like can fix much of that, but with too many too fast, ignoring users from general tags fast enough to keep the tag what you're hunting may become unfeasible.
I'm wondering about this "interest clogging" too, like if people start spamming a single interest. It seems like it won't affect the feed (which I guess is solely determined by shares of followed people), but it could be a problem if you search for #interest.