If you are mining for fun only then why not...

Some things to bear in mind.

1.  The laptop will get very hot as the GPU is pushed to it's limits
2.  The screen can go unresponsive if you are using certian mining programms and the settings are too high (you need to maintain the main OS GUI)
3.  Mining can cause some software and hardware problems ( especially if used long term).... I have burnt out 3 XfX 7970's in 5 months (says more about the quality of XfX tho tbh).
4.  You will not be able to use the laptop for much else while mining.
5.  You will not make any profit unless you have free electric.

you may want to concider a cpu only coin as the laptop to desktop gap is smaller for CPU perfomace over GPU perfomace.

consider primecoin or quarks .