If it were 15, I would have to put the kind of thought into picking friends that I put into picking words on Twitter. 50 seems merely inconvenient.
I doubt more than 50 people care about my personal photos anyway. It doesn’t sound limiting enough to make it a new kind of thing. I could easily be wrong.
Punctuation that I have to remove from a tweet doesn't have feelings that get hurt.
The "Twitter guys" had a reason to make twitter use 140 characters since twitter initially was built solely for use with SMS and they had to deal with SMS's 160 character limit. 140 for the tweet and 20 for your twitter handle. As others have stated 50 is an arbitrary number.
"We chose 50 based on the research of Oxford Professor of Evolutionary Psychology Robin Dunbar, who has long suggested that 150 is the maximum number of social relationships that the human brain can sustain at any given time. Dunbar’s research also shows that personal relationships tend to expand in factors of roughly 3. So while we may have 5 people whom we consider to be our closest friends, and 20 whom we maintain regular contact with, 50 is roughly the outer boundary of our personal networks. These are the people we trust, whom we are building trust with, and whom we consider to be the most important and valued people in our lives."
You are right on in this comparison. The limitation may be brutal, but it is simple and effective. Path is an "inner circle", and people should think of 50 as a high number they are unlikely to ever reach.
Good point - limits sometimes gives very interesting results.