Is ignorance bliss or is it worthwhile to stay informed?

I had a conversation with my friend about this. I used to think that it was best to stay informed but sometimes I'm not so sure. I have donated money and time to charities and I vote in local and national elections but sometimes it feels pretty useless. No matter who you vote for (left, right or independent) when they get into office money exchanges hands and they no longer stick to their views they campaigned on due to being bought off by interest groups involved with wealthy corporations. There are horrors going on around the world that I can do nothing about aside from giving some money. It seems that coming "unplugged" from current events might truly be bliss. Being ignorant might truly be worthwhile because being informed and not truly able to change anything gives one a feeling of hopelessness and helplessness. My friend says if you are informed you can change things, but can you really? Old systems of corruption are in play and it's truly hard to change a "well oiled machine". Does anyone else feel this way?