The recent death of 92-year-old Olive Cooke, Britain's oldest British Legion charity poppy seller, highlighted a dark side of our business we rarely confront. Following allegations that Mrs Cooke was 'hounded to death' by charities begging for money, the press has raged about unscrupulous fundraisers, with the British Prime Minister promising tough action to protect the vulnerable.

Regardless of the actual circumstances surrounding Mrs Cooke's tragic death, public hostility to some companies' more strident activity is clearly very real. Everyone has a favourite story about annoying fundraising techniques. Mumsnet has over 6,000 threads devoted to them. According to the Fundraising Standards Board (FRSB), complaints about fundraising have increased by 55% over the past two years alone.

Google data is revealing. Start typing 'charities are' and Google offers suggestions based on the most popular search terms: 'scams', 'businesses', 'corrupt', and so on. So why do people find charity marketing so annoying? Partly it's just a question of volume. According to the FRSB, Britons were exposed to over 20 billion fundraising messages last year. More important is the way those messages are targeted. Charities have become notorious exponents of the 'loyalty' approach to marketing, which says that the easiest way to make money is to screw more of it out of your existing customers. Give money to a charity, and requests immediately follow. The more you give, the more you are asked for. Little wonder that people like poor Mrs Cooke feel 'hounded'.

Charities are not alone in this. One of us ordered a small Christmas gift online once for a niece. It was ridiculously overpriced, and arrived late. But she was delighted, so we were happy. Until the emails started, that is. The company has emailed once a day ever since in the misguided belief this would keep us 'loyal'.

Intrusive media are another source of anger. The harder a channel is to ignore, the more virulent the reaction, with telesales and paid street fundraisers ('chuggers') at the top of the list. But their intrusiveness is the very attraction to users. To fundraisers, they just work. Well, maybe they generate short-term cash, but what's the long-term brand effect? Nobody knows, because nobody measures it.

Again, charities are not alone in being blind to the negative effects of marketing. We once worked on a leading bank's credit card. It had 5 million users who were mailed a monthly statement. Keen to maximise return on mailing costs, the brand printed an 'offer' every month on the envelope flap. A whole department was dedicated to finding items to flog in this way – ranging from nasal hair clippers to thigh-firming devices, we recall.

The response rates were very low (less than 1%) but were still high enough to make money. The client seemed surprised when we asked what the 99% of non-responders felt about these tacky offers? Surely they cheapened the bank's professional, responsible reputation? They didn't know though. They'd never asked. But one customer we asked likened the practice to 'going to see your bank manager and them standing up and trying to sell you the chair they were sitting on'.

Maybe the real problem here is one of measurement. Direct, short-term benefits of hard-sell marketing techniques may be easy to measure (and indeed easy to overestimate). But the long-term damage they can do to your brand among the silently fuming majority is much easier to ignore, and may not be apparent until it is too late.

Market research doesn't give enough weight to these issues. Less time measuring 'brand loyalty' and 'brand love', and a bit more attention to 'brand annoyance' and 'brand hatred' would benefit us all.