When viewed from a long enough timeframe, technology is always changing. This limits the lifespan of any given implementation of an application. Some applications are meant to have a short lifespan, but most are intended to live on. One reason to start with a design process that culminates in a requirements specification (SRS) is to create a company asset. When technology changes, the SRS can be used to "replatform" the application. Otherwise, there is design information obscurely embedded in the legacy code.
Another source of technology risk is from technology "churn". Many software technologies are continuously being created and promoted. The vast majority of them will fade away. Others will be hot for a while before fading away.
There is risk of selecting an immature technology for a software project. Conversely, there is a risk that everything looks like a nail, when the only tool one has is a hammer.
Mitigating these risks requires engineering judgement and a significant familiarity with technology options.
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