Just when you thought that music-discovery site Pandora swiped the last of the single-letter ticker symbols, along comes Zillow to grab the tail end of the alphabet.

The real-estate website that turned home ownership into a sticky online diversion is set to go public this week under the "Z" ticker symbol, and investors can't seem to get enough of Zillow. The company that was hoping to price its debut at $12 to $14 when it originally filed to go public three years ago raised its target on Friday to between $16 and $18.

You know something's wrong when a profitless dot-com devoted to the moribund real-estate industry (of all things!) is running into heavy demand from the prized clients of the offering's underwriters.

After all, online real-estate portals are dead. Market Leader, ZipRealty, and Realtor.com parent Move (Nasdaq: MOVE) are all trading for $3 or less. Even in the seemingly bubbly Chinese market, China Real Estate Information (Nasdaq: CRIC) and leading real world agency E-House (NYSE: EJ) hit fresh lows last month.

What makes Zillow so special?

Well, in this case, it pays to take a closer look at the numbers. Zillow is booming in popularity, despite homeowner indifference. There were 17.3 million average unique monthly visitors to its site during the first quarter of the year, 86% ahead of the crowd checking out their "Zestimate" home value estimates a year earlier. The number of real-estate agents paying a monthly premium to reach out to Zillow's growing audience has more than tripled over the past year.

Revenue climbed 74% to $30.5 million last year, accelerating to deliver a 111% top-line spurt during this year's freshman quarter. Losses have been narrowing every year since 2008, and the company appears to be on the cusp of profitability.

This doesn't mean Zillow is a bargain. With roughly 27 million shares outstanding after the IPO, we're talking about a company that will be valued at nearly $500 million if it prices at the high end of its range. Spoiler alert: It will -- if not a buck or two higher.

The bullish scenario here is that Zillow's scalable model will flourish when the real-estate market finally bottoms out. It has certainly gained ground during the lull.

The network effect is totally at play here. The same recipe behind eBay's (Nasdaq: EBAY) success in the late 1990s -- with buyers flocking to where the sellers are and vice versa -- is happening at Zillow within its admittedly narrow but highly lucrative niche. Realtors know that Zillow is the place to be if you want to find folks either looking to buy a new home or just curious as to what their digs would drum up in a sale. I have always felt that you can find the prettiest stocks in the ugliest places, and Zillow -- while not cheap -- fits the bill.

Will you be buying or passing on Zillow's IPO this week? Share your thoughts in the comment box below.