Any harm to delayed fermentation?

Is there any harm if it takes 2-3 days for active fermentation to start?
Does it matter if it's a lager or ale?

2-3 days lag time happens quite often and people don't report any problems.

On it's self it's not a problem but a quick starting ferment is preferable for several reasons.
The main ones are the sooner you get the fermentation going the less chance infections and wild yeast have a chance to take off.

agreed.

a slow start time is more of an indication that yeast pitching wasn't adequate. so, it could be an area for improvement.

maybe not enough yeast.
maybe pitched too warm, or too cool (shocked)
yeast was old.
lack of oxygen in the wort.

a starter helps with volume of yeast cells, and helps old cells repopulate too.
i use a wine whisk in my bucket to get air in the wort. i'm not sold on an oxygen tank w/ airstone...yet...

and just make sure you pitch at the ideal temp range...usually the same as fermentation range, so the yeast doesn't have to adapt much.

I've never encountered any issues with my slower fermentations and i have had some take 48+ hours to get going. I will say that my faster fermentations have resulted in better beers, but only to the extent that a true beer geek would notice.