I've pitched WLP007 direct from the vial at room temp with no ill effects. On their web page it says:
While a starter is not always necessary, White Labs recommends making a starter if the Original Gravity is over 1.070, if the yeast is past its "Best Before" date, if you are pitching lager yeast at temperatures below 65F, or if a faster start is desired.So if your yeast is in date, your OG's below 1.070 etc etc ...then you can go ahead.
Cheers - Louis MacNeice
Whilst this is mostly true, you have no idea of the conditions of how the yeast has been handled on it's journey from the States across the pond if you are based in the UK, what temperatures has it been subjected to? What is the variation between the fluctuations? What has the storage sanitation been like? Has the viability been affected and have yeast cells died from stressing?
That's why you should always grow a yeast when you get it or at least make simple starter for it on the brew day. Restore the viability and encourage the growth of the healthy yeast left.