How much percent of your daily revenue do you spend on CPC programs? My forum/article site started growing in size/revenue and I decided it would be best to spend a high portion of my income (50-80%) on google CPC, MSN Adcenter, and Overture. Will this investment pay off? It feels like a relative ripoff when articles in the newspaper are free and are more effective than a month's worth of CPC advertising (although articles in the newspaper will create a lot of initial interest and a lesser amount of prolonged interest -- this may be true with CPC programs but its harder to guage).
It also sometimes feels like a waste to be shelling out 20-30 dollars a day. In addition, the more I spend on these programs, the higher the CPC.
What's the best percentage/amount to spend on advertising?