There's no doubt that Dell's $1,000,000 of Twitter revenue is good ... something that points to Twitter as a possible sales channel (from Venturebeat via SmartBrief).
Now for the bad news. Dell generated $63,000,000,000 last year. This means that Twitter sales represent 0.0016% of annual revenue.
Let's say you are as successful as Dell is, but you manage a $50,000,000 business. 0.0016% of $50,000,000 is $794.
Somebody might blast me for this analysis, suggesting that something like 80% of volume is B2B, therefore excluded from Twitter. Let's go with your assumption. Now the comparison results in $4,000 for your average $50,000,000 business.
I am not criticizing marketing via Twitter, nor am I criticizing Dell, who is clearly innovating. About twenty percent of recent visitors to this blog come from Twitter, so I understand how the micro-channel can be used in a beneficial way.
I am simply asking you to carefully study the magnitude of the numbers the media share with us. Be willing to consider any bias in the information, and how that bias benefits those who write the articles.