Don't kid yourself about small companies. Unless you're the owner, you're a fungible cog everywhere.
In fairness, anyone can leave at any time. Your employer, regardless of size, has to be prepared for the possibilty that you'll quit for a better job, or for some other reason. It would be inadvisable to get emotionally attached to employees.
The reason you're less likely to get laid off at a small company is that small companies don't have the capital to hire indiscriminately, so they're less likely to have large inefficiencies. The number of employees is already as low as they can get away with, given their current revenue, so only a significant downturn in revenue would justify layoffs.
Smaller companies also have a hard time hiring. A bad hire for your 7th employee is way more painful than for your 1000th, and you can't afford to spend to much time interviewing. If employee 7 does a good job and jives with the team, they'd be foolish to throw them out. Though I'm sure there genuinely are many small companies run foolishly out there.
Small companies (whether VC-funded or bootstrapped) have their own issues. They tend to be different from what you see at big companies but they're certainly not nirvana.
In fairness, anyone can leave at any time. Your employer, regardless of size, has to be prepared for the possibilty that you'll quit for a better job, or for some other reason. It would be inadvisable to get emotionally attached to employees.
The reason you're less likely to get laid off at a small company is that small companies don't have the capital to hire indiscriminately, so they're less likely to have large inefficiencies. The number of employees is already as low as they can get away with, given their current revenue, so only a significant downturn in revenue would justify layoffs.