Is it right (assuming for a moment I have the relative light/heat efficiencies right) that if a light fitting can be used safely with a 60w traditional bulb then it could also be used safely with a 300w energy efficient bulb - as both would produce 50w of heat? And given how bright a 300w energy efficient bulb would be, even if you could buy such a thing, that there is now almost always no practical limit on the power of energy efficient bulbs that can be fitted to any light fitting?
You've been given the 'short answer', so now for the 'longer' one .....
One would expect what you say to be the case, and to a large extent it is, but the situation is, in fact, somewhat more complicated than that.
You will find fittings which specify 'maximum wattages' specifically for CFLs and/or LEDs which are surprising low in terms of your logic above. One of the reasons is probably the question of where the heat is generated, and where 'it goes'. With traditional incandescent bulbs, the majority of the heat generated is (like the light) radiated into the room - as one can tell by holding one's hand in front of such a bulb.
With CFLs and LEDs, the actual light producing elements produce little heat. The heat that is produced by such lamps/bulbs is primarily produced by the internal electronics, situated close to the base, and little is radiated directly into the room (again, put your hand in front of one!). Although the amount of heat produced is a lot less than would be the case with an incandescent bulb of similar light output, a lot of what heat
is produced is therefore conducted through the base, into the socket and other parts of the fitting. The potential thermal damage to the base/fitting is therefore proportionately greater than one would be the same with an incandescent bulb of the same wattage.
Light fittings are increasingly coming with 'maximum wattages' stated for particular types of lamps/bulbs, in which case it makes sense to follow the recommendations.
Kind Regards, John