In many ways, these two things are very similar. Both require managing people (in my guild I usually managed from 25 to 50 people at any given time). Both require that the leader needs to go all out to maintain things, otherwise you never know when things will fall apart. Both require that you make people believe in you, so even in tough times (and maybe 99.99% of guilds and startups will go through these) people will stick around long enough for things to get better. Both are fragile: people quitting, leaders burning out, setbacks in goals… any of these can result in the failure of the organization. Both require leaders that are resilient, diligent, able to overcome disappointments and setbacks, willing to learn, willing to work with people, etc. Both force their leaders to develop any of the above skills they start out lacking. That is, if either of them are to result in success.
There are differences too.
The main advantage in leading a guild vs. leading a startup is: the financial issue. When you’re leading a guild, there’s no pressure to make enough of a profit to pay your employees or satisfy you investors. This is a huge advantage. Even if you fail with your guild, you won’t be broke, or in debt, or know that you’ve seriously hurt the financial situation of your employees.
The main disadvantage in leading a guild vs. leading a company is: the financial issue also. When you’re leading a guild, you can’t use money as an incentive to accomplish anything or to keep anyone around. The people you manage can easily leave or screw you over, and there is little incentive for them not to. When an employee is a bit unhappy, it’s probably not enough for them to quit on you. Money raises the threshold of mistakes you can make as a leader, or unhappiness you can create in your employees: as long as it doesn’t get too bad, they’re going to keep sticking around and collecting their salary. In a guild, however, just a tiny bit of unhappiness can be enough for people to leave: so-and-so was rude to me, if you don’t deal with this by tomorrow, I’m not going to be coming back (this has happened to me multiple times, two of which are still extremely vivid in my mind); your policy regarding how we deal with such-and-such situation was a bad idea, I’m doubtful of the leadership here, I’ll be leaving.
I’ve been socializing more recently, and whenever I mention what I did to build and maintain a guild, people tend to tell me that even though I’m a gamer, I sound like an entrepreneur or a company director. And yes, though there are significant differences, even I’m a bit surprised at the skills leading a raiding guild in WoW requires, and forces you to learn.