It depends on the type of load. Motors will typically draw more current at lower voltage (since power remains constant for an induction motor) and could theoretically sustain some damage.

This link has a nice simplified discussion of brown-outs:

http://en.wikipedia.org/wiki/Power_outage

LFR1100 Actives,QS10HPx2,QS8x2,EP800,M3x4,M3x2 (Wood),M5HPx2 (Wood),AxiomAir,ADA1500-8,ADA1500-7