There have been questions on ELU about the pronunciation of can and can't in American English. This question is about the usage of the word, not simply its pronunciation.
Here are a couple of examples found on google:
- "Can help but to revert ...";
- "Could care less" (admittedly, this phrase also has other plausible reasons for being);
If contraction 't (apostrophe-t) was simply missed occasionally, it could simply be excused as poor proof-reading. However, the omission seems to be more widespread in popular usage. The root word (e.g. can) still retains its original, positive meaning, so a sentence such as "I can do that" is now at risk of being ambiguous - can is then its own antonym.