What purpose does the colon builtin ':' serve?

I've hacked on a lot of shell scripts, and sometimes the simplest things baffle me. Today I ran across a script that made extensive use of the : (colon) bash builtin. The documenation seems simple enough: > : (a colon) > : [arguments] > Do nothing beyond expanding arguments and performing redirections. The return status is zero. However I have previously only seen this used in demonstrations of shell expansion. The use case in the script I ran across made extensive use of this structure: if [ -f ${file} ]; then grep some_string ${file} >> otherfile || : grep other_string ${file} >> otherfile || : fi There were actually hundreds of greps, but they are just more of the same. No input/output redirects are present other than the simple structure above. No return values are checked later in the script. I am reading this as a useless construct that says "or do nothing". What purpose could ending these greps with "or do nothing" serve? In what case would this construct cause a different outcome than simply leaving off the || : from all instances?