I have good reasons. When a tool deal is posted on SD or another deals site, people order insane quantities, like it's free money or something. People just see the price, hear that it's a good deal, and just BUY BUY BUY.
A lot of SD forum members order quantities to resell on ebay and elsewhere, and others buy without knowing anything about the tool(s) other than the price is good.
Because of this, if I need to go back and order something I'd like to actually use, the price will either be inflated, or the item will be unavailable for weeks or months at a time.
Then there's another issue. Most of these bits are not going to be 1/8" shanked. People are going to be ordering and returning them by the dozens once they find out they don't fit the standard Dremel collet. Dremel does offer other sized collets, but many of the deal-grabbers won't know or care, they'll just know that the Foredom "Dremel" bits they ordered don't fit. Amazon will eat the return costs and might then jack up the price of the bits.
So it's not that I didn't want to share the deal, I didn't want the deal to be ruined for those who search for and buy bits to use by those who buy for resale or just for the sake of the sale.