Some people can spell, some can't.........I don't believe that people's poor spelling should be criticised in general - if we understand what they mean, what's the problem? There are exceptions, of course - public notices, news reports on TV, signs in shop windows.........things like that really should be spell-checked first and I don't think there's any excuse for not doing that. A bus stop outside a large shopping centre near where I live has the word 'buses' spelt as 'busses' - that infuriates me!
And a news report on a local TV station yesterday had the word 'occasion' spelt with a double 's' - for goodness sake!!!