Trichinosis is something you don't want to get:
...but there are plenty more:
Cooking meat properly (165F/70C) kills most things in it. You should always have well cooked meat when pregnant or have a low immune system.
A recent study in Australia found that almost all store bought chicken (raw) contained various traces of salmonella due to cross contamination in handling and processing. I'm assuming the UK and US are exactly the same (as farming and handling is similar). As most abattoirs are shared, getting grass-fed beef can't guarantee you aren't getting contaminated meat.
Symptoms of listeriosis include fever, headaches, vomiting and diarrhoea and left untreated it can cause meningitis and blood poisoning.
Listeria infections can be successfully treated if diagnosed quickly, but infants have a high mortality rate even when antibiotics are administered.
Infections during pregnancy greatly increases the risks of miscarriage, birth defects and newborn illnesses.
You can also get E coli or listeria from meat which is not cooked properly or left out after cooking.
Although most strains of E coli are harmless, some cause severe illness and occasionally it may lead to death, especially in the elderly or very young children.
I'm not game to risk my kids lives, so couldn't justify feeding them raw meat. I don't have any desire to do it myself either. It just seems unnecessarily risky.
I don't think you run a very high chance of getting sick and some people do it for many years without problem, so at the end of the day it's up to you. You just need to know that you are more at risk...
You might get some more info here (though a bit one sided
I eat my meat well done and do not have a compelling reason to do otherwise.