If wildflowers are weeds with good press agents, Spanish needles needs to get a better one. Bidens alba var. radiata is probably the most used butterfly nectar flower (see http://www.regionalconservation.org/beta/nfyn/plantdetail.asp?tx=Bidealbaradi), as well as the larval host plant for dainty sulphur butterflies. The small white flowers are often the only nectar source available in the winter. Still it is called a weed or even a noxious weed and the natural inclination seems to be to pull it out or otherwise get rid of it.
The problem is the seed which gives the genus its name Bidens, bi meaning two and dens meaning tooth in Latin. This two pronged seed seems especially designed to catch in clothing and animal fur. In fact, that is the design; this is the method by which it spreads.
Spanish needles have been used in many ways by humans: a tobacco substitute, to make medicines to treat colds and flu, hepatitis, bacterial infections, inflammation, and urinary tract infections. It is also being examined as a cancer treatment. The flowers and young leaves have been used in salads and the mature leaves can be boiled or steamed for greens. The flowers can be used for tea or to make wine. It has been suggested that Spanish Needles was one of the inspirations for Velcro. Supposedly the inventor was inspired by the seeds that stuck in his dog's fur. Observing how the seeds stuck to loops of fabric and fur he conceived the idea of binding two materials reversibly in a similar fashion.
References:
Atlas of Florida Vascular Plants, Bidens spp. http://www.florida.plantatlas.usf.edu/Results.aspx
Floridata, Bidens alba http://www.floridata.com/ref/b/bide_alb.cfm
Adventures of a Transplanted Gardener, No Need to Beg for Beggarticks, by Ginny Stibolt http://www.sky-bolt.com/beggarticks.htm
Bitterroot Restoration, Uses of Bidens alba http://www.bitterrootrestoration.com/health-care/uses-of-bidens-alba.html