Revelation 3
14 And unto the angel of the church of the Laodiceans write; These things saith the Amen, the faithful and true witness, the beginning of the creation of God;
15 I know thy works, that thou art neither cold nor hot: I would thou wert cold or hot.
16 So then because thou art lukewarm, and neither cold nor hot, I will spue thee out of my mouth.
17 Because thou sayest, I am rich, and increased with goods, and have need of nothing; and knowest not that thou art wretched, and miserable, and poor, and blind, and naked:
18 I counsel thee to buy of me gold tried in the fire, that thou mayest be rich; and white raiment, that thou mayest be clothed, and that the shame of thy nakedness do not appear; and anoint thine eyes with eyesalve, that thou mayest see.
19 As many as I love, I rebuke and chasten: be zealous therefore, and repent.
20 Behold, I stand at the door, and knock: if any man hear my voice, and open the door, I will come in to him, and will sup with him, and he with me.
21 To him that overcometh will I grant to sit with me in my throne, even as I also overcame, and am set down with my Father in his throne.
22 He that hath an ear, let him hear what the Spirit saith unto the churches.
Can an individual be labeled as lukewarm, or does it only apply to the church as a whole? Well, what is the church made up of if not individuals? The problem starts with the individual, and if you have enough individuals together, the whole church has a problem. One of the things about Revelation, as with any Bible prophecy, is that there is always more than one meaning to a passage. So in all likeliness this passage can apply to both individuals and the church.
Another thought is to consider that each of the seven churches represent a church age. Laodicea is the last church age, when the church becomes "lukewarm" at best.
What is a lukewarm person or church like? They are fencesitters. They refuse to take a firm stand on issues the Bible clearly states are wrong. They sit above everyone else on the fence, never helping or joining one side or the other. Good ol' Sunday Christians who never bother to dirty their hands or give of their hearts. God says he will vomit (spue is to vomit) them out of His holy mouth. They are the people raised in the church, been going to church all their lives, and have no idea who God is or what the Bible really says. They are usually prudes, acting so pious but with little inner faith. They are content in their mediocrity, never rising higher. We are commanded over and over to persevere in the faith and to study the Word.
Matthew 24
12 And because iniquity shall abound, the love of many shall wax cold.
13 But he that shall endure unto the end, the same shall be saved.
2 Timothy 2
15 Study to shew thyself approved unto God, a workman that needeth not to be ashamed, rightly dividing the word of truth.
What happens to hot water if it's let sitting in the open air with no heat source? It grows lukewarm, and then it eventually becomes cold. That is what happens to the lukewarm. They slowly become colder and colder. They are like the seed that fell on rocky ground - they grew fast but soon withered away.
As a church, lukewarm churches are complacent and passive. They pick and choose the scriptures they like and forget about the rest. "God is only love" churches are lukewarm. Such churches refuse to acknowledge that God has rules and not all will be saved.
Matthew 7
21 Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.
22 Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works?
23 And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.
Lord Jesus, more perfect and pure than the best of mankind, had to go through trials, temptation, pain, and death. Do you really think His followers will be required of any less? You are either committed fully to Christ, or you are not. The lukewarm ones will not be accepted.