Showers for babies are such a touchy subject and it always comes back to the gifts. Consider a wedding registry and wedding. Not many balk at a couple funding a wedding themselves these days. Certainly the bride and groom ask for items for their wedding presents - it's not like their MIL is picking out their new bedroom linens. And I think an argument can be made that they don't NEED a panini press while a new mom certainly NEEDS a carseat. Whether someone hosts your shower or not, the mom to be is usually putting together her own registry so aren't you already asking for gifts for yourself?
With my son's shower my best friend very kindly offered a location as we were living in a studio and to throw the party for me - and then shattered her ankle on vacation and was restricted to the couch for the better part of 4 months. Between her medical bills and being laid up just a couple weeks before the party- who do you think organized, prepped and PAID for it? Should I have cancelled my shower 2 weeks before? Ultimately I felt better about doing it myself than having someone do it for me. I felt putting the party on and doing so out of my pocket was a good way to thank my friends and family that were so generously (and gladly) gifting for the arrival of my son. Honestly, I would have been ostracized by my family and friends if I didn't have a party!
To me it's all really circumstantial - take good consideration of your local family and friends. If they would be offended, it's probably not worth the stress. But my take on showers? Hosted by the parents? Co-ed? Go for it! My biggest no-no's are if you have registered then under no circumstance may you have a pot luck. Never register for items that are for household use (stereos, tv's, etc.) Don't ask for gifts as well as a diaper trade-in for booze, make them part of the registry instead and the party should match the registry. Asking for a $1500 stroller? You better not be serving $5 frozen pizzas. In short - use as much common sense as possible :).