Flagging anyone has a negative effect on the flagger as it consumes the flagger's voting power which can be used for gaining author or curation rewards or self rep boosting.
A flag has a positive effect on the value of Steem as it helps preserve the rewards pool, but unless the flagger has a considerable portion of all Steem in existence, the negative effect surpasses the positive effect.
If you referred to an automatic decrease of the flagger's reputation or steempower, then the answer is no.
Retaliation by the flagee does have a negative effect on the flagger.