Even with all the interesting designs Vettel has from Troy Lee Designs (or is it someone else?), He still has this logo visible:
A small logo on the back of the helmet is what you consider visible? The only time you'd see that is when he isn't in the car and a camera happens to be looking at his backside!
No, currently the only reason you know its Vettel is that its not Mark Webber's helmet!
Its usually the cars that help me out because the numbers (something the onboards always help with since they are right there on the nose).
Yeah, um, the race number is not uniform across all cars though. Some teams display it quite visibly (recently Mercedes and Williams have made it quite clear). But other teams make it impossible to see. For most cars, you cannot see the race number except in from a top-down front view and an exact side-on view.
Not exactly brilliant track-side.
I would totally support the FIA mandating that race numbers are clearly visible on the cars though. It would be nice, but unfortunately the most visible areas (wings, sidepods, engine cover) are the most lucrative for sponsors..unless you're HRT
Of course, you could always get a mobile device with an app if its hard for you tell since it seems damn near everybody has one
Yes, I'm going to watch a car fly past at 200mph and look down at a phone at the same time am I?
No, I'd like to be able to watch the race. Not stare at a screen. Kind of defeats the point of being there? And you're also missing the point I'm making here - we're moving further and further away from spectators being able to follow the race with their eyes. Its seems a bit silly for people to pay all that money to go to a race only to then be having to stare at a tiny screen instead to work out whats going on. Its just a little backwards no?
You could maybe do it for the first 10 laps or so when the field is together and you're waiting for them to come around again - but at that point its also the point where its least confusing. Its later when the field separates out and pit stops happen that it becomes confusing. That's when you need to be able to not only watch with your own eyes but also tell who is who without having to stare for 30 seconds trying to make out tiny numbers, t-cams or messy helmet colours.
Fortunately we haven't got to the point where we have 2 drivers changing helmet every race, just Vettel. But I don't think its that weird for people to want to see more consistent and distinctive designs.