It is a grey area, but there is a difference between selling occasional personal items on eBay and selling for profit.

BBC: NEWS | Business | When does eBay selling become taxable?

Occasional sellers of personal items do not need to pay tax.

BBC: Tax form

And with Best Buy and other big boxes dominating the large items, RadioShack is left as little more than an occasional destination for batteries and power adapters.

FORBES: Magazine Article