Despite the fact that marketers are now using – and, in some cases, heavily replying upon – social media platforms like Twitter to target and connect with consumers, the latest industry research and leading expert opinions suggest that email marketing remains leaps and bounds ahead of social media marketing when it comes to overall engagement and effectiveness.

Most marketing on Twitter is aimed at raising brand awareness which is several steps removed from the holy grail of advertising — brand loyalty. That’s the beauty — at least from a marketers’ point of view — of email: start a rewards club, send your customers an email regularly with new offers, and measure the results. It’s a little more complicated than that, but essentially it’s easy to understand and to measure.

“The channel that gets the best satisfaction rating from advertisers is email with a 68% rating,” observes Paul Ausick of 247WallStreet. “On-site ratings and reviews tie with search marketing at 66%, and a branded forum comes in with 65%. Word-of-mouth marketing garners a 62% satisfaction rating.”

“On the eve of its initial public offering, Twitter’s lack of profitability is giving pause to some of the enthusiasm for what is likely to be the biggest IPO event of the year,” Ausick adds. “To keep advertisers happy and to attract more, Forrester says Twitter needs to do more than just provide the opportunities for advertising, it needs to give marketers the tools and help they need to get the most out of their ad dollars.”

Shares of Twitter are expected to price late tonight at between $23 and $25 a share. At the end of the day, this will give Twitter a valuation of approximately $17.6 billion, the richest valuation of any U.S. IPO.