Challies has an excerpt from a sermon by Charles Spurgeon regarding people who get messages from the Holy Spirit. Here is a small sample:
I have seen the Spirit of God shamefully dishonored by persons—I hope they were insane—who have said that they have had this and that revealed to them. There has not, for some years, passed over my head a single week in which I have not been pestered with the revelations of hypocrites or maniacs. Semi-lunatics are very fond of coming with messages from the Lord to me and it may save them some trouble if I tell them once and for all that I will have none of their stupid messages. When my Lord and Master has any message to me He knows where I am and He will send it to me direct, and not by mad-caps!
Read the Challies article here.