Any useless species?

A question sent to the Guardian's answer board: Are there any genuinely pointless species in the world which, if they were extinct, would have no material impact on the food chain or general homeostatis? Surely no one would miss wasps, for example. 
A quick glance through the comments provided no good answers in TPP's view, so here goes.
What a pointless anthropocentric perspective you have!  Species aren't there for humans, although many aren't here any more because of humans, and some have benefited from their interaction with us.  All species interact with some other species.  When a species goes missing, one or more interactions in the great network of being are lost and the fabric of life unravels a little bit more and becomes a tiny bit more fragile whether we would notice this difference or not.  Your question illustrates one of our great problems.  Humans see themselves as apart from nature rather than part of nature, and to place values on nature from just a human-perspective is just wrong.  And, yes, you would probably miss wasps, although probably not directly. 
Any readers want to provide an answer?

Botanical mutants

Meristemi points to an interesting blog featuring all manner of misshapen fruits and vegetables which is quite amusing. Saw another collection of similar images once that were all chosen for their similarities to genitalia, sort of a modern twist on the doctrine of signatures. Also, it’s good to know what amount of cucumber curvature is allowed in the EU. And as usual she makes an interesting point; the pursuit of fruity perfection has resulted in less diversity. The best tasting tomato the Phactor has ever sampled was a greenish red variety with a lobed fruit, far from round, red perfection in appearance, but isn't it taste that matters in a tomato? Although in a few cases like the Buddha's hand or Ugli citrus fruit, the misshapen has become a virtue. Maybe they're just hard to stack.

Mostly Unicellular

In Doug Adams’ Hitchhiker’s Guide to the Universe the entry for Earth gets updated and revised based upon 15 years of field research from “harmless” to “mostly harmless” (also the title of his 5th book in this series), not a vast improvement, but probably helps with the publisher's liability issues. The Phactor thought he was the only person who could do so much field research and publish so little. When teaching about biological diversity even biology majors seem surprised by the idea that a dispassionate, unbiased evaluation of Earth’s biosphere could be summed up similarly as “mostly unicellular”. This is true although it does seem a bit ridiculous from our large organism point of view. People just cannot or will not come to grips with the idea that each and every one of us has more microorganisms living in and on us than we have cells in our body. Wonder how much the modern obsession with cleanliness and resulting germaphobia have contributed to this misconception, or is it simply that most people just don’t know how tiny and how numerous are the organisms that surround us?