So, for example:
* There's an "embargo period" during which you're censored, you need to shut up, can't post your article. Preposterous.
* In many venues, you need to use custom links to Elsevier's "Science blocked and obfuscated". I mean "ScienceDirect"... yeah, right...
* You seem not to have rights to post new versions, or other derivative works.
* Stuff I haven't thought of because I'm not an IP lawyer.