Is it OK to present a URL using a link shortening service such as bit.ly? The reason I'm asking is that I think it's a lot easier to enter this URL (e.g., if you read it in a paper) as opposed to full URL. Or is this a bad idea?
A better alternative is to use a DOI if one is available. The providers of a DOI are supposed to ensure that the DOI is always up to date and points to the correct resource and as such a DOI is a better insurance against link rot than the original URL itself. DOIs are available for most recent papers (at least the ones I know of) as well as data etc. hosted on for example figshare and Zenodo. Apart from such resources, DOIs are generally not available and in that case I also recommend using the original URL directly.