If there is success there are is always the possibility that someone wants a piece of the pie. The same goes for ‘big audiences’. The bigger the audience, the bigger the chance that somebody would live to take advantage of that audience.
That is the core for hackers. They like to focus on mass, because that is the place where they are most likely to succeed. And that is where malware comes from. When your site gets ‘hit’ by malware, Google will not like that and it could affect your visibility in search engines. So you have to be careful not to get hacked. There are many things to look out for in that matter. Google has made a video in which they try to help you get started protecting your site. Useful and something each webmaster should at least take in mind.