Preface: What we're talking about is probably biochemically impossible (truly no bad side effects, no tolerance, etc.). So, everything that follows is a fun thought experiment, and should be taken as nothing more.
Let's say someone produces a true wonder drug that is relatively easy to produce and produces extreme happiness 100% of the time, with no side-effects, and no diminishing returns due to drug tolerance. This drug produces more happiness than any other activity that we could be pursuing with our time. As a result, all anybody wants to do is take this drug all day.
The author presumes that this is a bad thing, but let's question that assumption.
If everyone is completely happy 100% of the time, and - more importantly - happier than they would be if they were doing whatever it is they would be doing with that extra ambition, why should we assume that this is a bad thing?
Of course, somebody would need to maintain production of the drug. This means that people either would take it only part of the time, to maintain enough ambition, etc. to produce the drug on their own, or (more likely) we would have some lucky people who take it all the time and are always happy, and a few people who are tasked with producing all the joy for the rest of the world.
This exact premise (the second version) has already been explored, in short story form. http://en.wikipedia.org/wiki/The_Ones_Who_Walk_Away_from_Ome...
(I agree that this situation sounds bad - most people would have a negative emotional reaction to it, but it's fun to explore why we have an aversion to the thought of pure, unmoderated happiness.)