A dialup-access business, a social network… why not add a flower business? United Online (NSDQ: UNTD), the ISP and parent of Classmates.com has announced the acquisition of FTD, the floral products company, for $800 million. FTD shareholders will receive a combination of cash, stock, and United Online debt worth $15.08 per share, representing an 11 percent premium to yesterday’s closing price for the company.

So what’s the idea here? The announcement touts a more diversified revenue stream for UNTD—that’s certainly true. It also sees an opportunity to market flowers to UNTD’s customer base, which it claims has similar demographic characteristics to FTD’s customers (that one is a bit strange). Altogether, it expects improved scale and that it will be accretive to earnings in 2009. If there is analogy somewhere, consider Liberty Media (NSDQ: LINTA), which has combined communications, media and various transactional business. Even still, this is a surprising buy. Basically, the company is making a big move to dilute the impact of its declining ISP business. Release | Webcast (10:00 AM ET)

—Separately, United Online came out with a strong preliminary earnings report, which explains why the stock is up strongly this morning, despite the deal (normally, you’d expect UNTD stock to get crushed after announcing an acquisition such as this one). It now expects Q1 revenue of $121-$21.8 million, compared to a previous range of $116-$120 million. Op income guidance is way higher, at $19.9-$20.5 million from $11.8-$15.8 million. The announcement doesn’t discuss the drivers of the strong results. Release.