Retrofuturist's response is not quite correct. There are two [at least! I am not sure where the 'Dhamma-Follower' and 'Faith-freed' fit in] sorts of Sotapana mentioned in the Suttas: One who is such as a consequence of having awakened the Dhamma Eye, that is, he has seen that whatever has come to be is subject to ending, and one who is a 'Faith-Follower'.
The former has broken the first three sanyojanas (yokes to rebirth) which subject one to the possibility of rebirth in lower realms.
The concern for the latter with regard to the possibility of rebirth in lower realms is a matter of maintaining faith. Presumably maintaining faith he is reborn in a human or deva state conducive to further progress the first step of which would be the developing of the Dhamma Eye.
The distinction is in the matter of having broken the sakkayaditthi, or the holding of points of view with regard to individual existence; or, the other way around, having seen the truth of the Four Truths and understanding the implication with regard to the idea of self: that is, that there is no thing there that can justify the idea of 'I am' or 'This is mine'.
A couple of references that are right at my fingertips. Unfortunately no digital translations of these suttas are readily available:
EDIT: Here are a couple of discussions concerning this issue you may find interesting:
http://obo.genaud.net/dhammatalk/bd_dha ... etters.htm
http://obo.genaud.net/dhammatalk/bd_dha ... iduals.htm
Here is one that spells out the full meaning of faith and aserts without reference to the sanyojanas that this person is a Streamwinner:
KS 55.2, PTS, Woodward, translation:
Monks, blessed with four things an Ariyan disciple is a stream-wmner,
not doomed to the Downfall,
one bound for enlightenment.
Herein, monks, an Ariyan disciple is blessed with unwavering loyalty to the Buddha, thus:
He it is, the Exalted One, Arahant, a fully Enlightened One, perfect in knowledge and practice, a Happy One, world-knower, unsurpassed charioteer of men to be tamed, teacher of devas and mankind, a Buddha, Exalted One.
He is blessed with unwavering loyalty to the Norm, thus:
Well proclaimed by the Exalted One is the Norm, seen in this very life, a thing not involving time, inviting oneto come and see, leading onward, to be known for themselves by the wise.
He is blessed with unwavering loyalty to the Order, thus:
Walking righteously is the Exalted One’s Order of Disciples, walking uprightly, walking in the right way, walking dutifully is the Exalted One's Order of Disciples: namely, the four pairs of men, the eight sorts ofmen. That is the Exalted One's Order of Disciples. Worthy of honour are they, worthy of reverence, worthy of offerings, worthy of salutations with clasped hands, — a field of merit unsurpassed for the world.
He is blessed with the virtues dear to the Ariyans, virtues unbroken, whole, unspotted, untarnished, giving freedom, praised by the wise: virtues untainted (by craving or delusion), which lead to concentration of the mind.
Blessed with these four things, monks, the Ariyan disciple is a stream-winner,
one not doomed to the Downfall,
one bound for enlightenment.
Thus spake the Exalted One.
Having thus spoken, the Happy One, as teacher, said this: Whoso have faith and virtue, loyalty And insight of the Norm,—in time they win The bliss in which the holy life is steeped.