Many tech PR heads are this week making the annual pilgrimage to Barcelona for Mobile World Congress (MWC), an event that comes at a particularly opportune time for the communications industry. After all, we have reported on no less than four smartphone brands that have either changed or are looking to change their PR agency arrangements: Samsung, Blackberry, Motorola and Nokia. What is driving all of this flux? Some of it is undoubtedly cyclical, befitting an industry that is relatively trigger-happy when it comes to reviewing its public relations support. A look at some of the trends coming out MWC, however, points to some deeper, underlying issues. While smartphone sales are soaring, many expect a gloomy mood at the event, thanks to the lukewarm reception that has greeted some of the sector's key technology innovations, such as 4G, near-field reception and location-based targeting. Against this backdrop, it becomes easier to understand why so many mobile brands are rethinking their consumer engagement efforts. Three of the brands mentioned above - Blackberry, Nokia and Motorola - are in various stages of disorder, legacy giants that have found themselves overtaken by the smartphone revolution. For all handset makers, the window of opportunity, as far as smartphones are concerned, is small and closing fast. We are effectively in the midst of widespread adoption of these devices. Once that nears 100 percent, the game reverts back to a much less innovative playing field - defined by customer churn, pricing and services. It is not surprising, therefore, that many of these brands are feeling under pressure. It is unlikely that they will have a similar opportunity to redefine themselves for a considerable period of time; missing out now could consign them to irrelevance or worse. And even if they are able to come up with a winning product, an inadequate consumer engagement strategy can scupper any thoughts of success. No wonder their PR firms are feeling a little uneasy.