I've seen two people leave for new jobs lately at work, headed to startups. Their reasons vary, but they deliberately were looking for new businesses in their early stages. Startups are a very different animal than a giant corporation.
It got me to thinking about the variety of company flavors that you can work in. They all have their pros and cons, and I've never really thought about them. I've more or less gone from one job to the next (often not by choice) without much regard to the kind of the company I was going to. Microsoft is the one exception... I went to that one because, well, because it's Microsoft.
So let's start at that end. There is the giant, public company. The first one I worked at, Penton Media, wasn't that big, but it did trade on the NYSE. And of course, Microsoft is quite public, and quite large. They have/had a lot in common though. The pressure of shareholders can sometimes be detrimental to making the right decisions, and the older the company, the harder it is for it to change. On the other hand, it's often amazing how well endowed they are. If they do want to try something new, there's a lot of infrastructure to support it, and all of the normal overhead (HR, accounting, etc.) is already in place.
Next step down, the medium to large company that isn't public. Sometimes they have investors, sometimes not. It doesn't seem like there are many of these in technology circles. I've worked for a few in contractor scenarios. They remind me a lot of big companies, only without the infrastructure. They tend to serve a niche, and are often risk averse. In my experience, they're the least interesting places to work, because of the dull, non risky nature. I put small, established businesses in this category as well.
Startups are a very interesting beast. I personally define a startup as a company that has not yet reached a profitable state. These companies are agile, experimental and often filled with more enthusiasm as than you can handle. The downside is that they're also often immature and there's an expectation to abandon work-life balance. Of the two startups I've worked for, one fit that bill, but the other was actually pretty reasonable, and generally a solid company to work for. It was also surprisingly risk averse.
Then there is the non-profit. I've never worked for one, but have known quite a few who have. That has to be a strange position, because you certainly will be invested in the organization's cause to some degree, but you also don't want to starve just because you're working for an entity not existing to make money. I imagine that's quite fulfilling, but not always financially rewarding.
Government is another scenario, and it comes in many flavors. Local municipalities and school districts are the smallest units (counties too), and the politics can be a bitch, because, well, they're actual politics. Local government is most closely watched because of the small number of constituents, and elected officials are notoriously victims of small pond/big fish syndrome. Despite this, it can be pretty solid work, if you can deal with the politics. I haven't worked for state or the feds, and I imagine they have different kinds of problems.
Finally, there is your own company. I have one of those by accident. It's not the same as a company that has employees and risk. It's something I'd love to try some day, but I'm fairly terrified of being responsible for the livelihood of others.
What's great about this variety of company scenarios is that there's something different to learn at each of them. It's an interesting exercise to take inventory of what you've learned from each.