Sign of the times: Iowa-based publisher Thaddeus Computing is killing its 11-year-old Smartphone & Pocket PC magazine. In its place, the company will publish a new title, iPhone Life . Why the change? It's not about which phone is more popular. It's about advertisers.Publisher Hal Goldstein says that despite 20 million Windows Mobile phones sold in the past year, there's not enough of an ad market for Windows Mobile. Microsoft and cell-phone companies aren't willing to spend on ads in the mag. Moreover, he says, today's smartphone makers aren't like the old PDA companies — think HP — who were willing to bundle a magazine with their products. Goldstein has obviously sniffed out an iPhone accessories ad market to replace his no-longer-subsidized Pocket PC coverage.