I own a little of this. I am pretty serious about diversification in various sectors, various types of investment vehicles, and investing around the world.
I own area and country specific funds partially as a dollar hedge and in the belief that every dog or area of the world has his day so to speak and hot money flows around the world almost too fast for me to get in early unless I am already there.
I do quick analysis of stock or funds but I limit my risk by limiting what is allocated.
That being said, I follow well over 200 stock and funds and will probably max out around 300-400 holdings. Unless you like investing, have a bit to work with, and use a low cost discount brokerage this doesn't work for most.
I tell people I am more a shepherd of my investments than an active investor.
That being said, most of the gain in the stock market comes from the few stock that grow and grow and grow over decades. If I am to win that lottery I better own a little of it, and not sell if it doubles or triples.