In theory . . .
Studies have shown it is important to separate direct sound (speaker to listener's head) from reflected sound (bounced off side or front wall [and yes, ceiling and floor can be considered although they may not be as important]) by 10 ms or more to avoid sonic smearing. Fortunately sound travels at approximately 1 foot per ms, thus 10 feet becomes the desired minimal additional distance of travel for reflected sounds.
This applies to all speakers, except for wall or corner mounted designs, and is most often discussed relative to sidewall placement. Those placement recommendations calculate a distance from the speaker to the primary sidewall reflection point, then to the listener's head, by adding 10 feet or more to the direct sound distance.
The same principle applies to dipole radiators, such as Maggies, when recommending placement distance from the front wall. Because of the reflected sound, a distance of at least 5 feet from the wall achieves the 10 feet or 10 ms delay.
In practice . . .
Of course, many room set ups may not accommodate moving speakers 5 feet or more into the room. As others have suggested, absorption or dispersion products then become more important with these closer placements.
Now you need to ask yourself, how many "ideal" parameters can any of us satisfy if we don't have a purpose-designed room installation? Great enjoyment may still be found with less than perfect set ups. Just maximize your situation the best you can.
