What would cause the same beer to taste different I noticed that a beer in the bottle tastes one way and the same beer served to me in a cup elsewhere tastes different.  First, I thought the temperature difference would cause the taste difference, but no.  I also thought that the cup the beer was served in would change the taste, but no.  I tried this a couple of times and couldn't figure out what was causing the taste difference.
There are several things going on here.  

1) Temperature absolutely plays a difference in beer taste. 

Too Cold


  The biggest issue with beer served too cold is the way the temperature masks many flavors and aromas. The cold temperature slows the volatilization of aromatic compounds causing them to linger in the beer. When these compounds are not released, it dramatically changes the apparent flavor and aroma of the beer, sometimes to the point where it may come across as thin and tasteless. (American Homebrewers Association).


Too Hot


  Warm beer, on the other hand, does allow for more of the flavors and aromas to come to the forefront, but as beer approaches room temperature the sensations from hop bitterness and carbonation can decrease, which can lead to an almost flat-tasting experience. (American Homebrewers Association).


So here are suggested temperatures for serving various types of beer. 

....................Beer ................................. Suggested  Temperature

American Mainstream Light Lagers...............     33° – 40° F / 1° – 5° C

Pale Lagers, Pilsners ...................................   38° – 45° F /  3° – 8° C

Cream &amp; Blonde Ales     ...................................40° – 45° F / 5° – 8° C

Nitro Stouts    ...................................................40° – 45° F / 5° – 8° C

Belgian Pale Ales, Abbey Tripels    ..................40° – 45° F / 5° – 8° C

Wheat Beers     ................................................40° – 50° F / 5° – 10° C

Lambics     .......................................................40° – 50° F / 5° – 10° C

Dark Lagers     .................................................45° – 50° F / 7° – 10° C

American Pale Ales &amp; IPAs   .........................45° – 50° F / 7° – 10° C

Stouts, Porters     ............................................45° – 55° F / 7° – 13° C

Strong Lagers   .............................................50° – 55° F / 10° – 13° C

Real &amp; Cask Ales ...................................... 50° – 55° F / 10° – 13° C

Belgian Dubbels     .........................................50° – 55° F / 10° – 13° C


Data from Tasting Beer by Randy Mosher.

2) Glassware makes a HUGE difference. The shape allows for nucleation sites, temperature control of beer, aromatic release/retention. (See /user/MDMA's full response to my question about glassware and beer here)

3) What type of beer is it? If it is a nano brewery, it could be several things (wild yeast, inconsistency in brewing process, fermentation time, bourbon barrels stored in, etc.).

4) What was your drinking environment the first time/subsequent times you drank? Have you ever eaten somewhere for the first time while starving and with good friends you haven't seen in a while? That food will forever be amazing in your mind. You go back years later with a normal appetite and people you see regularly and the experience can be very different.