There is an interesting post on Zenit about the de-sacralisation of Churches. Fr McNamara says that there is no liturgical act to "deconsecrate" a church only a canonical statement or document.
Last night I stayed up later than I should and watched a television programme about an eccentric Dane, Mr Vig, who wanted to hand over his rather ramshackle castle to a group of Orthodox nuns, they wanted to turn a room into a "Church", he wanted it "consecrated" temporarily, so they could then build a proper Church. The nun said, "Once a church, a church forever", later she said "It would be a sin to change it".
I suspect this was the Catholic notion, hence an absence for any ritual to de-conscrate, unlike the Anglican, which of course grew out of a period in English history when churches were desecrated wholesale, almost as a national fad.
Personally I find it deeply sad when a church is turned into a museum, or a concert hall, a house, let alone a pub or a night club, casino or bingo hall.
For the Russian nun, I am sure the theology of consecration or blessing, was that once something was given to God it could not be taken back, this notion is found in the Old Testament of declaring something "Corbin". It is linked to sacrifice, sacrifice is not essentially about killing something, but putting it beyond human use. It is also linked in Orthodox thought to Covenant, God giving his promise to man and man giving his promise to God. God cannot take his promise back from man and man cannot therefore take his promise back from God. This is what underpins our theology of marriage, and the indelibillity of certain sacraments, and used to underpin such notions as oaths and solemn vows and promises.
The problem seems to be a loss of the notion of the "Sacred".