UBF's main purpose, which most ex-UBFers will recognize, and even UBFers themselves will agree with, is "disciple-making." The term "discipleship-training" is also used interchangeably. The program of "disciple-making" involves imitating what Jesus did in calling the twelve (later) apostles; namely, common life, Bible study, "history education," and preaching the gospel (world mission). There are two problems with having this as a stated purpose, aside from the fact that all authentic, born-again Christians wherever they are are struggling to be disciples of Jesus and to attract others to do the same, not just UBF.
First, the contradiction within UBF itself. All of the twelve disciples ran away from Jesus at the end (only one disciple unrepentantly betrayed Jesus). Jesus did not fault the eleven for this, however, but lovingly and mercifully sought them out after his resurrection. UBF, on the other hand, roundly criticizes anyone who leaves UBF for any reason, and makes it almost impossible for anyone to return, or at least to want to return. This is not only an incomplete imitation of Jesus, but runs counter to His own humbleness, mercy, and grace. UBF's conceited mind towards those who leave, usually expressed internally, is a problem they have yet to solve. Until it does so, there is much to be desired in its own description of itself as doing what Jesus did in raising disciples.
Secondly, and more importantly, "disciple-making" is impossible, humanly, if taken literally, as it often is in UBF. When did the disciples really become disciples? That is, in the sense of fully understanding Jesus and accepting His purpose for them, not to mention being enabled to do so? It was when the Holy Spirit was given to them at Pentecost, long after Jesus had gone back to heaven. UBF can have as nice and rigorous a program as they wish in trying to imitate how Jesus raised disciples, but this crucial element in "disciple making" will never be acquired by UBF, nor any other human. UBFers will answer that God is using them to make disciples. But sadly, too often its efforts to "make disciples" look more like pushing people to be Christian. Authentic calling and election are from the inside, a change in heart, through the action of the Holy Spirit and cannot be "made" by adherence to human training of any kind. There is something that is wrong with an organization that turns a deaf ear to so many people over the years who have experienced UBFers' "discipleship training" as pushy far beyond merely involving a set of high standards which are worthy and require effort to reach.
So, "disciple making" and "discipleship training" as expressly-stated main purposes are very naive at best, and grandiose or very dangerous at worst. If reformed Calvinist theology were truly followed in UBF, which it is not, although it is often purported to, then UBF leaders would have to step aside, and pull Samuel Lee aside especially, and let God be seen and glorified more clearly. This would, it is true, threaten UBF's very foundations as it stands, but in the long run would be the best for it, and help it to truly live for the glory of God, instead of one man.
That's all. Hope it wasn't too rambling. Thanks for reading!