In conversation with Pentecostals, I have found that the intensity of emphasis on this experience does tend to vary from "all can, even if they don't", to "all eventually will", to "all must".

However, for most of them, speaking in tongues is regarded as the infallible proof that they have received the Holy Spirit. 

It is the sign that God has accepted them. Some even go so far as to say that without this gift, no one is born again, or saved at all.

My problem with this "infallible proof" is that, judged by what the Bible really does say about tongues, it is not infallible at all! 

It is not infallible proof, when the "spirit" which inspires the experience, is clearly NOT the Spirit of Truth promised by Jesus. (John 16:13)

It is not infallible proof when it is accompanied by dangerous false teaching; about who Jesus is; about what the Gospel of the Kingdom of God is; about what the real Christian hope is; about the place and importance of baptism; and most important of all, about what repentance and real obedience to Jesus means.

It is not infallible proof in those who take to themselves a false sense of security from it, or whose lifestyle shows little convincing evidence at all, of the fruit which is the real mark of the Spirit's presence. (Gal 5:22-25)

It is not infallible proof when it is found in false prophets, accompanied by signs and wonders, by which even the elect are in danger of being deceived. (Matt 24:24)

It is not infallible proof in Catholics, who still hold to all the false teaching of their false church system.

No "spiritual" experience in anyone, even if real in itself, can ever be infallible proof of anything at all, when an identical but false experience is found in so many others.

Bible truth, from the Spirit of Truth, about speaking in tongues, is that it is NOT FOR EVERYONE. 

In 1 Cor 12:7-11, Paul makes it quite clear that it is one of a number of gifts given individually. Just as a human body is not all eye, or ear, or hand, or head, or feet, neither is there one single universal or indispensable gift for all. It is plain that NOT ALL are apostles, or prophets or workers of miracles. NEITHER DO ALL SPEAK IN TONGUES. (verses 27-31).

Any "spirit" which claims otherwise, is not the Spirit of Truth promised to those who love Jesus and obey Jesus.

We should be cautious about any who wrest the Scriptures to present us with a "lying wonder".