Investors know this story. The technology sector is the largest sector allocation in the S&P 500 and, this year, is the best-performing group in the benchmark U.S. equity index. Buoyed by the fortunes of marquee large-cap tech stocks, such as Apple Inc. , the Technology Select Sector SPDR is up nearly 19 percent year-to-date. Still, there have been concerns about elevated valuations in the technology sector and that the group has run too far too fast. While some market observers argue a sequel to the 2000 “tech wreck” is unlikely, some analysts aren't enthusiastic about the sector. In a note out Wednesday, AltaVista Research tagged XLK, the largest consumer staples ETF by assets and the most heavily traded technology ETF, with an Underweight rating.Source