Dogs can instantly pick up on humans who are afraid of them - it's all in the body language, scent, etc. My theory is that in that situation the dog's natural instinct is to try and 'dominate' the 'weaker' animal (human) which is why they make a beeline for the fearful human and fuss around them, although not necessarily attacking.
There's a stupid woman who is clearly terrified of dogs but who insists on taking her morning walk across our local off-leash dog park and of course she is always surrounded by dogs sniffing and fussing around her. She squeals and covers her head with her hands (weird stuff) so of course the dogs take even more interest. She was screaming at the owners to 'get them off, get them off' and someone politely suggested that she might like to chose from any number of other local parks where dogs are not allowed at all but she couldn't see the logic.
Another example is an over-protective mother who takes her 3yr old to the same park and whenever a dog comes within 50ft she scoops the kid up and starts making a fuss. Of course, the more noise she makes the more interested the dogs become and she's doing a great job in teaching her kid to be scared of dogs too. Take the kid to another bloody park you moron!