Stag and Hen Parties
Bournemouth for some reason has become the South Coast's Mecca for stag and hen parties. It's a "Chicken and Egg" thing as to how it became so - one factor must the availability of cheap hotel rooms out-of-season. The town centre has evolved in recent years to offer a lively bar and club scene and as the university and language schools have mushroomed the town centre is definitely a youngster's paradise in the later hours.
Bit of an old man's paradise as well as the scantily-clad women parade the streets - HA! But that's a digression ;)
Some of the hotels, bars and restaurants point-blank refuse this sort of custom, whilst others positively welcome it. Personally I reckon that the stag and hen crowds really enliven the city, and not just for the reason given above LOL. Many of the groups put a lot of effort into themeing themselves, adding colour and character to what can be a "bloody boring" town, and for the most part are reasonably well-behaved whilst being out to hedonistically enjoy themselves (and each other).
The pubs and clubs are well-policed by their licensed doorstaff and the Police themselves maintain a highly-visible street prescence and so despite the drunkeness there's rarely any serious problems.
The street cleaners do a marvellous job in clearing the night before's debris and so during the day Bournemouth gets back back to being a family-friendly "bloody boring" beach resort.