Starting a new business on the internet, people usually end up making the same types of mistakes. They do not plan out a number of things. Running an internet business is a much more accessible form of entrepreneurship than previous methods of starting businesses. You do not need as much an investment in your online business as you do not need to open up a shop and then market it, like you would have to a few years ago. However, the lower requirement of capital investment means that a lot of people do not actually fully plan out their business budgets and do not keep proper checks and balances in place when running the business. What happens here is that a lot of people end up not knowing what their expense burn rate is. They feel like that the money is not really being spent, but then end up spending more of the budget than they need to. This in turn leads to their budget being depleted faster than they earn more money.
Aside from not having a plan of expenditure vs potential and expected earnings, a lot of people try to be too general in their marketing plan. While the internet lets you reach an unprecedented amount of people for a really small price, the other thing that ends up happening is that people do not create a target audience for whom they want to aim their marketing at. So while you can reach a huge general audience you have no idea if any of them will even like your product or service. This is taught in a lot of recent online marketing training programs and seminars, you have to know who you are selling to even in the internet age.