As a counterpoint, here are Zendesk's icons with no text: http://imgur.com/a/wzCO0 -- can you guess what those do?
Of course, this is about the worst example of iconography I've ever seen so here's the same with the labels left in: http://imgur.com/a/CyqA6 and I'd even go so far as to suggest that given their choice of icons they should just get rid of them and make it text-only.