Folding bikes can make fantastic commuter bikes; as has been seen with a few entries on this list. With that being said, there is a potential concern with this type of a design. Some consumers may be suspicious of the strength of the frame and if it is compromised with an integrated folding feature. It depends on how the bike is manufactured as, to be honest, this actually can present itself as an issue. If it so happens that the folding bike pivots in the middle of the top tube then yes, this can actually weaken the frame over time.
But, if it is designed in the same manner as Montague folding bikes then this is not a concern. See, Montague incorporates a different design into their folding bikes and pivots them at the seat post to prevent the frame from being weakened.