Steal your business model. We don't have a shortage of business models, it's okay if you pick one that's already working for someone else.
Steal your web design. There will always be enough people brave enough to invent whole new ways of interacting online. But unless you're an interaction designer or your business model depends on something new, do us all a favor and use something that already works.
Steal your tools. You probably don't need to build a new email delivery engine, a new overnight shipping method or a new way to run payroll. Once someone has a reliable, cost-effective building block, feel free to use it.
When it comes down to the thing you will be known for, your uniqueness, your gift, your thing worth talking about--don't steal that. Writers shouldn't steal words from other writers, and chemists have no need to steal the research of other chemists. Sure, go ahead and invent.
For the rest, honor those that came before and use their work as a building block for yours.