More than a quarter of marketers went into marketing because they wanted to be creative, researchers have found. So why do so many B2B marketing efforts seem exactly the same?

The reason, in part, is that some things work well. In nature, convergent evolution leads different kinds of organisms to similar solutions when they work. The number of strategies that will lead to success is limited.

Marketers don’t simply echo the successful efforts of other marketers, though — they also parrot things that don’t really work.

You’d think in this era of analytics that marketers would be ruthless in killing off ineffective strategies. Marketers are often inexplicably fond of some of them, though, and they cling to them beyond the point of logic.

Writers understand this: The expression, “kill your darlings,” often is used to coach writers to exclude content or quotes they love if they interfere with the effectiveness of the story. It is a cruel business. So is marketing.

Here’s a sampling of some marketing darlings that need killing.

The ROI Calculator

Companies have target customers — types of buyers or businesses that are more likely to close and turn into long-term customers with tremendous lifetime value. However, to your ROI calculator — that simple little Web application that asks visitors for numbers and spits out an ROI number in return — every buyer is an ideal customer.

“Has anyone ever seen an ROI calculator that returns a negative number?” asked Greg Tapper of Topo at his company’s recent summit in San Francisco. “No! They all say that every investment always pays off, every time.”

There’s the problem: ROI is not simple. It isn’t based solely on the vendor information, or on information available to the vendor. Integration costs, the impact of implementation on employees’ work, and opportunity costs imposed by downtime are rarely part of the equation. Buyers get this: Why would the vendor include factors that would dim the rosy picture they want the buyer to see?

Buyers typically are not dumb. If an ROI calculator is offered, their assumption is that it is biased in favor of the business offering it, and that assumption is nearly always correct.

If you value buyers, be honest with them. Instead of a simplified spreadsheet that will deliver a positive number every time, give buyers something more open-ended — something that allows them to do a truthful examination of costs in their particular business context.

Suggestions about potential expenses allow buyers to consider their own situation and to draw real conclusions about the financial implications of a purchase. Buyers will appreciate your guidance — and when some get good ROI numbers…