Should we discourage nesting?

[should have thought about this sooner!]

There's been an open-fronted nest box in our garden for years which has been completely ignored by both us and the birds, until now.  We have a robin casin' the joint with some enthusiasm but she hasn't started building yet (as of 0800 this morning).  The male has been around for a couple of years and is very tame - he would be unphased by out presence but the female is much more flighty, and definitely would be.  The box is fairly exposed (in two months it will be well hidden in jasmine, but not now), about 1 m from the ground and about 1.5 m from a feeder.  As we are almost the only house on the road without cats, they all seem to frequent (and defecate in) our garden.  I'm wondering if we should actually remove the box due to it's exposure?  While it would be lovely to have lodgers, we're worried that leaving the box there is actually going to increase their chance of getting munched, or suffering nest failures.

Thoughts?