Agreed. Right now it is way to easy to abuse the flag feature.
Personally I'd recommend a system where users are given a limited number of flags a day based upon there Steem Power, or simply put into place a minimum reputation needed before being able to flag any post.
People do have a limited number of flags per day! Flagging is just reverse-voting, and if you flag too much your voting power gets used up.
Ppl with more steem power then yourself are also dangerous. They should state their reason for flagging and they should reconfirm a few hours later. When rethinking your reason for downvoting (after some time has passed) you will come to the conclusion that often it was not justified.