????不管投資前做了多少研究，等到交易時總還是多少需要一點信心。人們可能會嘲笑分析師的預測落空，但很多分析師盡管并沒有受到公司的壓力來粉飾預測，有時還是會失準。研究只能幫到你這么多。接下來需要的是猜測。

????鮮有股票能比亞馬遜（Amazon）更加依賴猜測。這家公司在發布數據或指標時堪稱小氣。亞馬遜賣出了多少部Kindle？這家公司不愿透露。它公布假日季的發貨量，但只限高峰日數據，不是整個假日季。亞馬遜網絡服務部門每年將賺取約38億美元收入，但該公司不會把這一塊獨立拿出來統計，幾年來一直是納入“其他收入”項目。要弄清楚這個部門的利潤率，挑戰就更大了。

????誠然，亞馬遜也提供業績指導區間【盡管像Facebook等其他公司最近幾個季度都閉口不談業績指導值】，但它提供的區間相當寬，寬到連UPS的送貨卡車也能輕松駛過。亞馬遜這個季度會公布營運利潤或虧損嗎？不錯。據該公司稱，本季度收益數據將介于虧損3.40億美元至盈利1,000萬美元之間。這樣的靶子，閉著眼睛都能投中。

????缺乏清晰明確的信息讓依賴基本面的投資者面臨艱難選擇：要么干脆不投資亞馬遜的股票，要么完全相信公司管理層能把事情做好。選擇后者的人近年來投資業績不錯。亞馬遜股價在過去5年中飆升了234%，同期標準普爾500指數（S&P 500）僅上漲了15%。

????亞馬遜要求投資者在其他方面相信公司的管理層。這家公司從不派息，堅稱：“我們想保留全部收益，為未來的增長提供資金。這也意味著亞馬遜持續保持低利潤率，有時擴張投入得多了，還會出現虧損。但亞馬遜收入的持續增長已經為它贏得了信賴。

????但有時，亞馬遜也會讓看漲的投資者陷入尷尬。亞馬遜一直強調自由現金流才是衡量公司健康狀況的關鍵財務數據，而不是很多投資者認為的標準衡量指標——每股收益。自由現金流基本上是企業創造的、超出需要保持其增長所需的那些現金。亞馬遜認為，這個指標能更好地衡量亞馬遜將利潤回報給顧客（而不是投資者）的策略是否成功。

????問題是，亞馬遜自由現金流的增長在過去12個月下降到了1.77億美元，同比驟減85%，主要是因為亞馬遜為西雅圖的新辦公樓支付了14億美元。但在自由現金流放緩的同時，收入增長也在放緩：上一季度收入同比增長1%，低于之前一個季度的5%和上年同期的12%。

????No matter how much research is done before an investment, there always remains a little bit of faith when it comes time to place a trade. People may mock analysts when their forecasts are off, but the analysts who aren't pressured by their firms to dress up estimates -- which is a lot of them -- still miss the mark sometimes. Research only takes you so far. After that it's only guesswork.

????Few stocks involve more guessing than Amazon (AMZN). The company is tightfisted when it comes to disclosing data or metrics. How many Kindles has Amazon sold? The company won't say. It discloses holiday shipments, but only on the peak day and not for the entire season. Amazon Web services will make an estimated $3.8 billion in revenues a year, but the company won't break it out as its own category, lumping it in with "other revenue" where it's been for years. Figuring out the division's profit margins is even more of a challenge.

????When it comes to guidance, Amazon does offer it (while others like Facebook (FB) have been mute on guidance in recent quarters), but it usually offers a range you could drive a UPS truck through. Will Amazon post an operating profit or a loss this quarter? Yes. According to the company, the figure will land somewhere between a loss of $340 million to a profit of $10 million. That's a dartboard any monkey could hit.

????The lack of clarity leaves investors who rely on fundamentals with an uneasy choice: either don't invest in Amazon's stock or simply trust the management that it will manage things well. Those who've opted for the latter have done pretty well for themselves. Amazon's stock is up 234% over the past five years, while the S&P 500 (SPX) is up 15%.

????Amazon asks investors to trust its management in other ways. It has never paid a dividend,asserting that, "We intend to retain all future earnings to finance future growth." That also means Amazon consistently has thin profit margins and sometimes slips into a loss when it's spending heavily on that future growth. But it's earned trust because it has so consistently delivered on growth in revenue.

????But it can sometimes put Amazon bulls in an awkward position. The company has always stressed free cash flow as the key financial metric to measure its health, instead of the earnings per share that is the standard gauge for many investors. Free cash flow is basically the cash the business is generating beyond the spending needed to keep growing. Amazon feels it's a better measure of whether Amazon's strategy of returning profits to customers (and not investors) is succeeding.

????The problem is, the growth in Amazon's free cash flow over the past 12 months fell to $177 million, an 85% drop from the comparable period a year earlier. That's primarily because Amazon paid $1.4 billion for new offices in Seattle. But free cash flow is slowing at the same time revenue growth is: Revenues in the last quarter grew 1% on year, down from 5% in the previous quarter and 12% in the year-ago quarter.