Source: businesslink.gov.uk Digital marketing is reaching a tipping point - some 17 per cent of companies surveyed by the Chartered Institute of Marketing say that online advertising spend has now overtaken offline spend. Computer company Dell claims it made US $3.5 million in less than six months from Twitter using a viral system. Discount offers are posted daily for its followers, who then frequently re-tweet the offers, so attracting new followers. A recent survey from Performics and ROI Research found that '44 per cent of Twitter users are happy to be alerted about promotions and special offers by the site'. Forty-eight per cent had responded to an advert they'd seen, and, perhaps most startlingly of all, some 44 per cent of those surveyed had themselves become an endorser by recommending products they'd seen to other users. .