Can it be useful to run a factor analysis for only two items? I have a data set with two items that potentially measure the same latent variable: personal well-being. Can it be useful to run a factor analysis (Principal Axis Factoring Analysis) on them, or does a factor analysis require more items?

With two items (variables) it's not likely that FA or PCA would be helpful.  In fact, aren't there usually multiple items required in order to derive a score for most of the scales (anxiety, depression, worry, etc.), based on the weighted sum of numerous e.g. Likert scores?
