The new tagging method is really annoying. I understand the need for assigning the proper tags on similar questions, but this means that I should already know the standard tags SO.
For example, I just tried to add the tag
regular-expressions to a question and I realized that there was no such tag on SO. I had to stop and think about what other tags would be appropriate and I found
regex. My complaint is that I shouldn't have had to think about this and SO should have recommended me other tags (including
regex) based on other people's attempts to create new tags.
This can be implemented by monitoring re-tags and finding tags that have been added to questions which had their tags deleted. I'm sure you will notice an outlining pattern. It's worth giving it a shot as it will help people to tag their questions properly and, based on their choices, the algorithm can learn to be even more precise.