Caches are basically data stored in our computers when we visit websites, logged in our online accounts, make downloads, etc. Clearing caches and stored infos in our web browsers once in a while is a helpful experience, but it works more than that for me.
I am a member of an MMORPG private server forum and aside form playing their in-game games, the administrators also host forum games. They have this voting method wherein you can collect points according to the number you voted for their site to be on top of the rankings list.
I don't know if the administrators think their users are not at all knowledgeable of the computer or perhaps they purposely left that aspect vulnerable, but their voting system can easily be abused.
After making a vote, it will generate a point for your account which you can eventually trade in game for goods. Goods are traded according to how high your voting points are. Although it was written there you can only vote "once a day", clearing the cache tells a different story.
Mozilla Firefox offers the option to clear everything. I tried that and tried to vote for the website with an interval of 2 minutes and voila, another point was given to me. I tried doing the cycle again and another point was up for my account again.
It wasn't my intention to abuse the system so I stopped when I learned how vulnerable their voting system is. Maybe the administrators of the website though they can trust their players of not cheating. But surely there will be a lot who will cross the border.
Perhaps that is the reason why a lot of relatively new players in the game are so rich!