[fadetree]

It's nothing to grind your gears over.

But yes, it's probably mostly a slang usage...I hope. The problem is that not everybody realizes it, especially non-english-first-language types, and so it can cross over from slang usage to being confusing. English is pretty crazy anyways, and that increases the need to be accurate when speaking or writing.
Bad English is spreading, I see terrible stuff often on supposedly journalistic outlets, like 'loose' instead of 'lose' and things that aren't even sentences. Problems with the weak verb construct are very noticeable - people say things like 'I have went' instead of 'I have gone', for instance.
Oh well, the other argument is that language changes anyway and so don't worry about it, but even a flexible language like English needs some kind of coherent core structure or otherwise you're just making crap up and it becomes impossible for people to learn. Core grammatical rules are there for a reason.