Some of these factors are network effects. I conjecture that every product has some kind of network effect; it's a question of degree. A telephone 100% network

Some of these factors are network effects. I conjecture that every product has some kind of network effect; it's a question of degree. A telephone 100% network effect; a USB drive might seem to have no network effects, but most people are biased towards the most popular one. I think your criteria of "explosively successful" might require very strong network effects - it certainly requires some way to reach lots of people, and network effects are one way of doing so (the de.li.ci.ous guy mentioned 3 needed factors, and this was one - he also put a new-to-me twist on it. I'll try to find the post). If you relax it to modest, steady growth, it might not require strong network effects (and possibly might be more stable - because resistant to explosively growing competitors...).