The jQuery script we use for placeholders is actually Simple Placeholder which is far less common (45 stars compared to 1,957 stars) than jQuery Placeholder. So when other plugins enqueue the jQuery Placeholder script there are some conflicts.
To mitigate this I just changed the handle from jquery-placeholder to jquery-simple-placeholder. Now if other plugins or themes use the mathiasbynens' version of the placeholder script there shouldn't be any problems.
See here: http://wordpress.org/support/topic/jquery-error-has-not-method-simpleplaceholder?replies=1
And here: https://woothemes.zendesk.com/agent/#/tickets/83703
fixing placeholder script's handle
updating enqueued placeholder script handles
@BFTrick Could just change scripts?
@mikejolley wouldn't changing scripts be a lot harder than just renaming the handle?
Is there any functionality in the more popular placeholder script that we would ever need?
@BFTrick They are both pretty much identical, so if one has better adoption, it makes sense to switch (if it doesn't cause any issues anyway).
Replace placeholder script. Closes #3586.