I work in accounting and it is fairly easy to find an accounting job if you are smart and hardworking. Different majors have different demand. If you choose to be in a very competitive field it is harder to find a job because there are less opening and only the best of the best will be chosen.
Also, some major are simply more specific and narrow than others. If you are studying astronomy you will likely have to end up in the astronomical field, whereas someone like me who studied accounting could likely move around to other business majors fairly easily because they are closely related.
If you have a major in mind try making connections early on in your college career. Getting an internship is a great way to gain experience and get your foot in the door at a company who could then offer you a job after graduation. This is one way to ensure that even if there a not a lot of job opportunities, you still end up in the field you want to be in.
While some may not end up in their chosen major, that's okay too! It may seem like you've wasted your time studying something that you aren't using but everyone has different experience and your diverse knowledge could bring something new to your company that will make you stand out amongst your peers.
It is also important to remember that your first job is not your last. Ask anyone in your life over the age of 60 to list all the jobs they have ever had. Some may be similar but I bet you will be surprised at how common it is for career paths to change over time.
Any advanced knowledge you attain will be helpful in your life. Even if you aren't using the specific facts you learned in college, there are other techniques and learning abilities that you will carry with you to any profession. Things as simple as study habits, time management, and organization, are all must haves in surviving college and will be important tools to any company as well.