The coming of the son of man had been planned from before the foundation of the world and news of His arrival had been 'leaked' in a steady and consistent fashion since the book of Exodus. We therefore should not be surprised to find, especially in His early ministry, that the Lord sought to control and regulate the manner and nature of information that was shared or transmitted about Him and His work.
It is an adage within modern media companies that, "There is no such thing as bad publicity". Going further, power and compassion are both powerful crowd motivators and thus miracles of healing would, as we see today, appear to be a perfect platform from which to launch a populist ministry. Thus the human instinct within us would expect the Lord to have mounted a PR campaign that sought to maximize exposure to the miracles he performed. We actually see the disciples go down this exact line of reasoning in John 7:3,4 where they suggest that the Lord should move more towards the center of action.
However, despite the very best of human reasoning, we discover in those same verses and in Mark 1:44 that the Lord was performing healings in a deliberately covert manner. The question, of course, is "Why?" The Lord answers the 'why' in John 7:6: His time was not yet come. The problem is that it isn't immediately clear which 'time' this refers to and why it hadn't yet come.
With most of scripture the key to interpretation is simply to read the verse before and after and in this case the following verse gives a vital clue. The Lord states that the world hates him because of His testimony. Any modern politician with a popularity poll that low would be extremely concerned. The Lord however, was content, even desirous of His lowly ranking. We must remember that His foreordained work upon the Earth was to die that we might be saved. Whilst a crowd shouting, "Hosanna" was allowed before His final entry into Jerusalem three years of such popularity would not have been a natural path towards a cross.
In fact we find the understated nature of the Lord's ministry to be prophesized. Matthew. Here we find that it was fully His intention to avoid as much of the fuss and commotion as He possibly could. We also find in this prophecy that there is a limit to this behavior. The limit is 'till he send forth judgment unto victory'. This limit is probably also the 'time' referred to in John. There will come a time when the Lord's greatness is to be visible, undeniable and irresistible for now he chose and chooses to work in a manner that is only really noticeable to those that search.
It is possible that the Lord's admonition of the unclean spirits is following in the same vein. He was deliberately being low-key and having the testimony of the enemy may have been too compelling. However, if this is the case, then v27 of Mark 1 suggests the plan partially failed. His ability to command and silence the unclean spirits became, of itself, a cause for wonderment. As I cannot readily believe a plan of the Lord would backfire I therefore have to believe that He commanded the spirits to silence to show His mastery of them.
Ultimately, we will not fully understand the reasons behind all that the Lord did and does until His time is come and judgment goes forth. However we can, I believe, know that from a biblical perspective there is such a thing as bad publicity. The Lord wills some information to be spread far and wide; other information is to be revealed carefully to those whom the Lord chooses. We live in a country with so much Christian literature it is almost possible to loose the blessing amongst the 'noise'. Let us pray for discernment in what we hear ourselves and it what information we 'publish abroad' to others.