Sadly, I've also had to close the most popular part of my web site due to lack of advertising.
At one time, I was receiving about $600/mo. in ad revenue, which when all was said and done, was simply meeting expenses... But every one of my ad carriers have cancelled or gone out of business with the sole exception of popuptraffic, which while actually paying out, was undercounting the impressions by some 500 percent. At the time I made the decision to close it, I was getting in excess of 900,000 pageviews per month, and collecting about $27 in ad revenue. My site was split across two servers to carry the heavy traffic loads and the expense was getting too much for me to take as a loss. But I'm certain I'm not alone. Hopefully, the ad agencies will one day get it through their heads that there are better ways of handling traffic than the current model they insist on using, and I'll be able to resume having content, but until then... It's 'bye-bye website'